0:00:00.029,0:00:07.089
it's a rude awakening and mornig welcome[br]to do with the uh... third week of

0:00:07.089,0:00:10.769
medical school for you you might have[br]noticed that our

0:00:10.769,0:00:13.679
cohort of medical students has that[br]doubled

0:00:13.679,0:00:17.081
in size if you guys have noticed you if[br]you're here first of all the job finding

0:00:17.081,0:00:19.078
this other lecture hall sorry work

0:00:19.078,0:00:22.034
jumping you from place to place but this[br]is part of

0:00:22.034,0:00:23.048
trying to revamp

0:00:23.048,0:00:26.779
all of our lecture halls and so we had[br]to do this in a stage process those of

0:00:26.779,0:00:28.529
you that understands gantt charts

0:00:28.529,0:00:29.769
and construction

0:00:29.769,0:00:32.046
will uh... will sympathize but you found[br]the place

0:00:32.046,0:00:35.689
in north lecture hall now are your[br]colleagues here and suits

0:00:35.689,0:00:39.018
they are a great source of advice

0:00:39.018,0:00:44.064
and uh... and uh... being able to and[br]sort of queries about different staff so

0:00:44.064,0:00:46.289
now you've got your built-in

0:00:46.289,0:00:50.219
counselors uh... here but they're also[br]going to be very busy as you notice they

0:00:50.219,0:00:54.009
probably probably noticed they started[br]about an hour before you did so

0:00:54.009,0:00:55.039
for

0:00:55.039,0:00:57.469
that's what you have to look forward to[br]it here

0:00:57.469,0:00:58.064
that that

0:00:58.064,0:00:59.053
uh...

0:00:59.053,0:01:04.022
hope you guys survived your first quiz[br]hopefully it wasn't too painful i know

0:01:04.022,0:01:06.009
many people ask will they be medical[br]decision making

0:01:06.009,0:01:10.015
stuff on the quiz and the answer to that[br]was

0:01:10.015,0:01:11.015
uh...

0:01:11.015,0:01:14.079
remember that genetics in pathology or[br]the big components of the quizzes and

0:01:14.079,0:01:18.087
that we in india and we have assignments[br]so you turned in your first assignment

0:01:18.087,0:01:20.909
last thursday at small groups

0:01:20.909,0:01:23.036
uh... i'm in the process of reviewing[br]them

0:01:23.036,0:01:25.088
they will get back to you in your mail[br]boxes

0:01:25.088,0:01:28.074
uh... so you will be have them to study[br]from

0:01:28.074,0:01:32.459
i will also when i return them to you[br]you should pay attention on c_ tools all

0:01:32.459,0:01:35.061
publisher ultimate which will also have[br]the answer key

0:01:35.061,0:01:37.419
to interview uh... assignments

0:01:37.419,0:01:41.159
so there's no hidden doctors here it'll[br]be a turkey will give you an explanation

0:01:41.159,0:01:45.189
to each of the questions that way you[br]can look at your answer what banter in

0:01:45.189,0:01:47.003
turkey was any notes that you had

0:01:47.003,0:01:48.909
and reconcile and if there are any

0:01:48.909,0:01:52.299
other questions certainly we're here to[br]help you

0:01:52.299,0:01:55.002
you have another small group tomorrow[br]afternoon

0:01:55.002,0:01:58.024
that will largely be based on material[br]that we cover today

0:01:58.024,0:02:01.067
uh... hopefully if you guys have had a[br]chance to get a jump start on that i try

0:02:01.067,0:02:03.009
to post in a week in advance

0:02:03.009,0:02:04.549
you're more then welcome to

0:02:04.549,0:02:08.014
uh... reading ahead is hopefully fine[br]encouraged if you want to do want to

0:02:08.014,0:02:09.006
that's totally fine as well

0:02:09.006,0:02:12.009
there should be enough time to be able[br]to complete that again it's the same

0:02:12.009,0:02:12.939
protocol

0:02:12.939,0:02:15.052
bring it to your small group still[br]discuss that with here

0:02:15.052,0:02:18.989
co students in your small group silkair[br]and then returned them

0:02:18.989,0:02:22.959
uh... tournament and then i'll be[br]returning to you in a timely fashion

0:02:22.959,0:02:29.065
any questions about the logistics of[br]this course for this part of this force

0:02:29.065,0:02:31.519
so why don't we go ahead and get started

0:02:31.519,0:02:32.699
uh...

0:02:32.699,0:02:35.929
today we're going to be for we're gonna[br]be picking up a little bit where we left

0:02:35.929,0:02:37.049
off

0:02:37.049,0:02:38.069
last time

0:02:38.069,0:02:42.091
and he wants start by declaring uh...[br]any industry relationships

0:02:42.091,0:02:46.046
that i might add to contacts that meet[br]your otherwise

0:02:46.046,0:02:48.209
in the answer is

0:02:48.209,0:02:50.569
certain factor

0:02:50.569,0:02:52.459
uh... dancers is i have not been

0:02:52.459,0:02:53.309
to disclose

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so nothing that would uh... interfere[br]with my ability to present you an

0:02:55.959,0:02:59.269
objective view of uh... medical decision[br]made

0:02:59.269,0:03:03.739
so our first just returning to where we[br]left off with their first thread

0:03:03.739,0:03:07.479
this is around information retrieval[br]focusing on asking in acquiring

0:03:07.479,0:03:09.169
if you remember and

0:03:09.169,0:03:13.239
after last monday we left off by talking[br]about the way the structure well

0:03:13.239,0:03:16.219
foreground question and these are sort[br]of that

0:03:16.219,0:03:18.789
uh... fundamental tools that were[br]required to

0:03:18.789,0:03:22.509
af but good questions get the[br]information from the literature and then

0:03:22.509,0:03:26.064
interpret and apply them as a way to[br]focus a little bit just to revisit

0:03:26.064,0:03:28.066
this tool that we talked about

0:03:28.066,0:03:32.006
this was the pico tool that encourage[br]you to just use it as a tool basically

0:03:32.006,0:03:36.006
it's a way of specifying the different[br]elements in your question there will be

0:03:36.006,0:03:36.909
important

0:03:36.909,0:03:40.027
tour it ought to be able to sort out the[br]appropriate answers

0:03:40.027,0:03:42.086
and we think it's important to be able[br]to do with in advance

0:03:42.086,0:03:45.009
because by doing it in advance

0:03:45.009,0:03:49.003
uh... you're really able to focus on[br]what you need and what your patients

0:03:49.003,0:03:49.079
need

0:03:49.079,0:03:54.087
so in order to practice doing this went[br]to ask you to do is to look at this case

0:03:54.087,0:03:56.087
and practice with your partner

0:03:56.087,0:03:58.239
jotting down the foreground

0:03:58.239,0:04:00.849
uh... question so let me go over the[br]case real briefly

0:04:00.849,0:04:03.072
because we're gonna be using this uh...[br]moving forward

0:04:03.072,0:04:06.006
so this is now this is a forty[br]two-year-old woman

0:04:06.006,0:04:09.559
who comes to her primary-care[br]practitioners office

0:04:09.559,0:04:12.084
for follow-up of her diabetes and you're[br]the medical student

0:04:12.084,0:04:14.006
she's currently on libby ride

0:04:14.006,0:04:16.609
ten milligrams twice daily

0:04:16.609,0:04:19.939
however her blood sugars still stay[br]elevated despite being on that

0:04:19.939,0:04:21.379
medication delivery right

0:04:21.379,0:04:22.919
after you see this patient

0:04:22.919,0:04:24.649
you're attending asked whether you think

0:04:24.649,0:04:28.028
she should admit foreman to her regimen

0:04:28.028,0:04:31.053
pretend like you know what would your[br]ideas and pretend like you know what

0:04:31.053,0:04:34.009
metformin is you may not but these are[br]both

0:04:34.009,0:04:36.058
uh... it is that we use in diabetes

0:04:36.058,0:04:39.034
we'll be right is the sole final you[br]react

0:04:39.034,0:04:42.909
and metformin is uh... another agent[br]that we use

0:04:42.909,0:04:45.011
uh... packets dvd

0:04:45.011,0:04:48.049
uh... and i cant really pronounce what[br]that actually stands for it's a very

0:04:48.049,0:04:50.027
difficult word to pronounce but

0:04:50.027,0:04:54.006
suffice it to say good beer i can see[br]his your um... insulin

0:04:54.006,0:04:58.053
uh... usa secretion but metformin[br]improves your sensitivity uh... to

0:04:58.053,0:05:01.084
insulin is well or that your body makes

0:05:01.084,0:05:03.052
so let's say you know all of that

0:05:03.052,0:05:06.053
and the question i would ask you to do[br]is to start putting on

0:05:06.053,0:05:09.088
your hat as if you were a clinician just[br]to get a sense of what

0:05:09.088,0:05:13.289
these kind of foreground questions are[br]about remember therefore important

0:05:13.289,0:05:14.569
components

0:05:14.569,0:05:17.929
for a foreground question you have to[br]define the patient population that

0:05:17.929,0:05:19.027
you're interested in

0:05:19.027,0:05:21.028
you have to define the intervention

0:05:21.028,0:05:22.819
that you're interested in

0:05:22.819,0:05:26.459
the comparison group that would be part[br]of the study that might help you answer

0:05:26.459,0:05:28.008
the question andy outcomes of interest

0:05:28.008,0:05:31.639
that you would be that you in your[br]patient would be interested in

0:05:31.639,0:05:35.046
this will help you then scanned the[br]literature to figure out what are the

0:05:35.046,0:05:38.002
articles that would be most relevant

0:05:38.002,0:05:39.849
for this particular case

0:05:39.849,0:05:43.000
so i'd like you did it was turned your[br]partner and come up with one

0:05:43.000,0:05:46.037
that would meet all four categories it's[br]a fairly straightforward exercise but

0:05:46.037,0:05:47.058
wanna make sure that you get

0:05:47.058,0:05:50.068
such answer practice that's so spent a[br]couple minutes doing that and we'll talk

0:05:50.068,0:06:21.949
about it

0:06:21.949,0:07:06.009
a

0:07:06.009,0:07:09.009
okay three parking lot with remember[br]that really

0:07:09.009,0:07:11.074
nobody answers here because

0:07:11.074,0:07:15.669
every single uh... every single answer[br]that you would give each of the four

0:07:15.669,0:07:18.037
different categories would have some[br]debate around

0:07:18.037,0:07:22.031
whether the article that you retrieved[br]with those particular characteristics of

0:07:22.031,0:07:23.041
the study population

0:07:23.041,0:07:25.036
would actually help you answer your[br]question

0:07:25.036,0:07:29.039
or not and the degree to which it would[br]do that so let's just hear some of the

0:07:29.039,0:07:33.044
questions what i'd like you to do is not[br]the same like he was ex and i was

0:07:33.044,0:07:34.055
uh... was why

0:07:34.055,0:07:37.008
i'd like to see if you could stated in[br]the form of a question one that would

0:07:37.008,0:07:39.319
contain all four

0:07:39.319,0:07:40.849
of those different components

0:07:40.849,0:07:41.719
just a little hint

0:07:41.719,0:07:45.077
i might ask something like this uh... on[br]one of the either the assignments

0:07:45.077,0:07:46.077
or certainly

0:07:46.077,0:07:52.099
while our final examination as well so[br]who wants to take a stab at it

0:07:52.099,0:07:54.949
them

0:07:54.949,0:08:01.078
uh...

0:08:01.078,0:08:04.199
okay great so here let me let me restate[br]this

0:08:04.199,0:08:05.084
in women with diabetes

0:08:05.084,0:08:09.939
what is the effect of metformin plus[br]glider ride

0:08:09.939,0:08:12.053
blood sugar levels compared to drive me[br]right along

0:08:12.053,0:08:16.019
so let's see if we got all the before[br]components in their is that patient was

0:08:16.019,0:08:20.059
women with diabetes your intervention[br]was metformin it would be right together

0:08:20.059,0:08:22.059
versus delivery right alone in the[br]outcome you're interested in

0:08:22.059,0:08:25.269
was improvement in her blood sugar[br]levels okay

0:08:25.269,0:08:28.339
so let's break that down the patient[br]population is that were women with

0:08:28.339,0:08:30.076
diabetes was that it did anyone have[br]something different

0:08:30.076,0:08:34.025
then women with diabetes here

0:08:34.025,0:08:39.019
awesome al you specified in age cutoff[br]so women with diabetes over forty ok any

0:08:39.019,0:08:39.759
other

0:08:39.759,0:08:44.002
variabilities there

0:08:44.002,0:08:48.002
asel na specifying gender so just all[br]patients with diabetes let's back up and

0:08:48.002,0:08:48.969
think about that

0:08:48.969,0:08:51.098
limelight it so that the question would[br]be if we're to get an article

0:08:51.098,0:08:53.000
that had

0:08:53.000,0:08:54.087
all ahead men and women

0:08:54.087,0:08:56.049
in the past study population

0:08:56.049,0:08:59.061
would we say that's ok to extrapolate[br]the results

0:08:59.061,0:09:01.859
and then apply to this patient[br]population

0:09:01.859,0:09:03.011
and so you said

0:09:03.011,0:09:07.086
potentially that would be ok any reason[br]to think that verb rationale

0:09:07.086,0:09:19.061
what goes through your mind as you're[br]making that call

0:09:19.061,0:09:22.069
but the answer being that date one of[br]the rationale might be fifty-year

0:09:22.069,0:09:24.058
defined studies where you have

0:09:24.058,0:09:26.063
both genders represented as opposed to

0:09:26.063,0:09:30.029
one gender alone so that's one certainly[br]one consideration what might be another

0:09:30.029,0:09:36.008
consideration you would use

0:09:36.008,0:09:39.056
uh... so now you're talking you're[br]getting even more specific saying

0:09:39.056,0:09:40.649
impatience

0:09:40.649,0:09:41.057
who are

0:09:41.057,0:09:45.032
poorly controlled on good be ride with[br]diabetes

0:09:45.032,0:09:48.065
what about the comparison group purses[br]uh... verses the intervention so that we

0:09:48.065,0:09:49.249
another

0:09:49.249,0:09:50.054
shape that you would be there

0:09:50.054,0:09:53.052
but that you might use backing up to the[br]gender issue

0:09:53.052,0:09:56.022
the question i would ask you to ask and[br]we ask this question all the time does

0:09:56.022,0:09:59.044
the disease manifest differently or act[br]differently

0:09:59.044,0:10:01.049
in one gender verses another

0:10:01.049,0:10:03.098
does the disease manifest if really[br]inpatient over forty

0:10:03.098,0:10:06.016
rice's those that might be younger than[br]forty

0:10:06.016,0:10:09.002
those would be the questions that you[br]would be asking yourself and remember

0:10:09.002,0:10:12.042
you have to build some background[br]knowledge about this subject before

0:10:12.042,0:10:14.063
being able to ask the most sophisticated

0:10:14.063,0:10:15.088
foreground question

0:10:15.088,0:10:18.041
i'm trying to know a little bit about[br]the pathophysiology

0:10:18.041,0:10:21.013
but it's reasonable to have those[br]different want uh... those those

0:10:21.013,0:10:23.239
different shades of variation

0:10:23.239,0:10:24.038
in the patient

0:10:24.038,0:10:27.022
the intervention was metformin plus[br]we'll be right did anyone have a

0:10:27.022,0:10:32.016
different intervention

0:10:32.016,0:10:34.065
oddly be what we're thinking about the[br]kind that we're not talking about

0:10:34.065,0:10:37.055
stopping the glitter ride and adding[br]metformin

0:10:37.055,0:10:40.052
but in some cases you might be looking[br]for head to head comparison

0:10:40.052,0:10:43.066
and in fact if you're thinking about it[br]from a drug company standpoint they may

0:10:43.066,0:10:46.041
be interested in head to head[br]comparisons because they're trying to

0:10:46.041,0:10:47.529
prove one

0:10:47.529,0:10:49.083
at the at the efficacy of one drug over[br]another

0:10:49.083,0:10:52.009
if you're thinking about it from the[br]standpoint of

0:10:52.009,0:10:55.045
of uh... pathophysiology you might be[br]interested in head to head comparisons

0:10:55.045,0:10:58.043
but if you're thinking about it in the[br]practical sense we often might be

0:10:58.043,0:10:59.022
looking at

0:10:59.022,0:11:02.054
adding and agent to an existing regimen

0:11:02.054,0:11:04.409
those are less commonly found

0:11:04.409,0:11:05.095
in the literature on just a tad

0:11:05.095,0:11:09.031
and so you may be stuck saying well i[br]don't have an additional

0:11:09.031,0:11:12.049
uh... i don't have a study that shows[br]the addition of metformin

0:11:12.049,0:11:14.007
and so you would have to extrapolate

0:11:14.007,0:11:15.389
from head to head comparison

0:11:15.389,0:11:16.078
which is tricky did you

0:11:16.078,0:11:19.008
certainly beyond the scope of this[br]course but keep in mind those of the

0:11:19.008,0:11:22.076
questions that we entertain as positions[br]as for reading the literature

0:11:22.076,0:11:26.059
now one of the outcomes that was was[br]mentioned was improvement in blood sugar

0:11:26.059,0:11:32.038
so first of all how would we measure[br]that

0:11:32.038,0:11:34.329
but voz votes

0:11:34.329,0:11:37.309
okay so you could be looking at that's[br]the blood sugar which have been one

0:11:37.309,0:11:40.075
marker of diabetes hemoglobin a one c[br]which alert next year

0:11:40.075,0:11:45.013
is a eleven for a test that we get that[br]it looks at patients long-term control

0:11:45.013,0:11:47.959
our blood sugar at least medium control[br]over the past three months

0:11:47.959,0:11:49.048
so that be a good outcome

0:11:49.048,0:11:53.017
to specify so you could get that level[br]of specificity and you might find

0:11:53.017,0:11:57.369
studies that look at just after larger[br]verses does that look at a one c and you

0:11:57.369,0:11:59.066
would have to decide which ones

0:11:59.066,0:12:02.068
for me in my patient now would be[br]important consideration

0:12:02.068,0:12:05.072
any other types of outcomes you guys[br]looked at

0:12:05.072,0:12:15.027
or anyone specified besides blood sugar[br]improvement

0:12:15.027,0:12:18.047
basil side effects might be another[br]outcome that you would look at what sort

0:12:18.047,0:12:21.089
of side effects might be worth we'd be[br]worried about a few

0:12:21.089,0:12:24.075
if you know any

0:12:24.075,0:12:27.082
so one that i might be worried about is[br]would i be dropping this patient's blood

0:12:27.082,0:12:29.059
sugar too low

0:12:29.059,0:12:31.032
to the point that they have hypoglycemic[br]events

0:12:31.032,0:12:32.097
so that would be something to be[br]thinking about

0:12:32.097,0:12:37.031
but absolutely remember this is a[br]therapeutic question that your asking

0:12:37.031,0:12:40.096
and as if they're peter question there[br]are unintended or sometimes

0:12:40.096,0:12:44.419
uh... known side effects of the[br]different genes that we

0:12:44.419,0:12:47.026
that we use and so looking at the[br]adverse events

0:12:47.026,0:12:49.011
would be another important outcome

0:12:49.011,0:12:52.009
so keep in mind this is just an exercise[br]but to wall

0:12:52.009,0:12:55.035
to get us to where we dot where we need[br]to go so that when we look at the

0:12:55.035,0:12:56.000
literature

0:12:56.000,0:12:57.499
we know what we're looking at

0:12:57.499,0:12:59.074
that is the point of the foreground[br]question

0:12:59.074,0:13:01.007
now this is up there

0:13:01.007,0:13:03.949
foreground question before i questions[br]about their feet

0:13:03.949,0:13:07.459
later on in this lecture really talking[br]about or run questions

0:13:07.459,0:13:09.061
as it pertains to diagnostic tests

0:13:09.061,0:13:12.369
again to get distinct types of questions

0:13:12.369,0:13:16.979
but both equally important here a couple[br]of examples that we that were uh... that

0:13:16.979,0:13:21.029
would be reasonable i think you guys[br]came in kimba up with these in tight to

0:13:21.029,0:13:23.098
die but if that was one thing we didn't[br]talk about the fact that this woman

0:13:23.098,0:13:25.089
is a tight to diabetic

0:13:25.089,0:13:28.061
she may be insulin requiring more[br]insulin

0:13:28.061,0:13:32.001
resist uh... you know that we talk about[br]that one person so i can fight one being

0:13:32.001,0:13:33.007
autoimmune

0:13:33.007,0:13:36.019
more likely to happen upon early onset

0:13:36.019,0:13:37.011
tight too

0:13:37.011,0:13:39.097
uh... not necessarily requiring insulin

0:13:39.097,0:13:42.589
uh... and so you might want to[br]distinguish that studies that you're

0:13:42.589,0:13:43.066
looking at

0:13:43.066,0:13:46.084
but then there's a question is metformin[br]good write better than the bread alone

0:13:46.084,0:13:49.075
in lower bucks ordered that was[br]something that you guys came up with and

0:13:49.075,0:13:52.076
here's the side-effect question among[br]women with type two diabetes

0:13:52.076,0:13:56.017
are there more instances of low blood[br]sugar of insufficient on both metformin

0:13:56.017,0:13:57.066
it would be right

0:13:57.066,0:13:59.036
when compared with we'll be right along

0:13:59.036,0:14:02.068
so that you guys came up with this[br]fairly straightforward exercised but

0:14:02.068,0:14:06.036
keep in mind level of specificity is[br]important because you're gonna be faced

0:14:06.036,0:14:08.011
with a ton of different studies

0:14:08.011,0:14:10.087
you're gonna have to work through to[br]figure out which are the ones that are

0:14:10.087,0:14:14.096
most relevant tumi and the patient that[br]you're working with what are the

0:14:14.096,0:14:17.051
important outcomes to that may be very[br]different

0:14:17.051,0:14:20.057
and the outcomes that you are interested[br]in and so it's important vehicle to

0:14:20.057,0:14:23.053
specify that of prop yes

0:14:23.053,0:14:25.379
went

0:14:25.379,0:14:27.072
at

0:14:27.072,0:14:31.899
so it literature doesn't exist uh...[br]what do you do that is probably

0:14:31.899,0:14:35.032
uh... the hardest question we face as[br]clinicians

0:14:35.032,0:14:38.008
there is a when i'm gonna ask you to i'm[br]not gonna be able to answer that

0:14:38.008,0:14:39.003
completely

0:14:39.003,0:14:42.099
but as we build our course over the next[br]three years what you're going to get a

0:14:42.099,0:14:44.008
sense of

0:14:44.008,0:14:46.076
is that there is a hierarchy of evidence

0:14:46.076,0:14:48.028
meaning that as

0:14:48.028,0:14:52.045
certain studies take on certain study[br]characteristics both in terms of how

0:14:52.045,0:14:56.092
they're designed and how well their[br]implemented the level of evidence that

0:14:56.092,0:14:59.086
they provide become stronger or weaker

0:14:59.086,0:15:03.028
and so it's not necessarily do i have

0:15:03.028,0:15:05.007
is there no studies out there

0:15:05.007,0:15:07.098
what are their studies out there that[br]are less well done and so what do i do

0:15:07.098,0:15:08.086
with those

0:15:08.086,0:15:10.094
compared to studies that are really well[br]done

0:15:10.094,0:15:14.061
keeping in mind that the studies that[br]are really well done are actually less

0:15:14.061,0:15:15.899
frequently encounter

0:15:15.899,0:15:19.079
and those studies that are not so well[br]done or studies that are

0:15:19.079,0:15:21.082
observation as opposed to control[br]clinical trials

0:15:21.082,0:15:24.043
so the answer your question is i don't[br]have the answer now but that is exactly

0:15:24.043,0:15:26.007
going to be the point of the next three[br]years

0:15:26.007,0:15:29.066
what do you do when you're faced with a[br]quandary we're gonna try to party

0:15:29.066,0:15:31.073
conceptual model that will on full

0:15:31.073,0:15:35.002
that you'll get more comfortable

0:15:35.002,0:15:38.066
there many sources the foreground[br]questions these are the pics precise

0:15:38.066,0:15:40.729
questions if you go to medline four

0:15:40.729,0:15:43.091
or that you will go to a practice[br]guidelines or you'll use evidence-based

0:15:43.091,0:15:46.139
databases and all of these sorts of

0:15:46.139,0:15:48.008
of uh... of resources will be introduced[br]to you

0:15:48.008,0:15:52.003
as we go through

0:15:52.003,0:15:54.081
so building on those questions then

0:15:54.081,0:15:58.879
we do need to then figure out what is[br]the data that we're getting and how do

0:15:58.879,0:15:59.093
we interpret

0:15:59.093,0:16:03.149
and so as i mentioned therapy types of[br]questions are

0:16:03.149,0:16:04.088
are very important part

0:16:04.088,0:16:07.019
of what we do is the nation's they seem[br]to be

0:16:07.019,0:16:10.579
the most natural thing you would assume[br]positions do which is prescribed

0:16:10.579,0:16:11.031
treatment

0:16:11.031,0:16:12.088
and figure out whether it's

0:16:12.088,0:16:14.043
making a difference or not

0:16:14.043,0:16:17.092
however it is not the most fundamental[br]thing that we do in fact

0:16:17.092,0:16:20.007
therapeutic questions are very[br]sophisticated questions

0:16:20.007,0:16:24.239
that we actually don't cover much about[br]their pete this year

0:16:24.239,0:16:27.084
we do it in your second year as you[br]start tackling pathophysiology

0:16:27.084,0:16:29.003
this year

0:16:29.003,0:16:31.008
the question we want you to start[br]thinking about

0:16:31.008,0:16:33.072
what is going on

0:16:33.072,0:16:39.023
is that you all a g of why what i'm so[br]the the clinical manifestations

0:16:39.023,0:16:40.042
of the disease

0:16:40.042,0:16:44.099
and so that really focuses on diagnostic[br]reasoning and diagnostic test and so

0:16:44.099,0:16:49.042
we're gonna spend the rest of our time[br]today focusing on diagnostic tests

0:16:49.042,0:16:52.087
so here are the learning objectives for[br]the rest of today by the end by the end

0:16:52.087,0:16:55.068
of this lecture and honestly by the end[br]of your small groups tomorrow because

0:16:55.068,0:16:58.082
you're gonna have to work through these[br]concepts in small groups it's gonna be

0:16:58.082,0:17:00.031
mainly a superficial

0:17:00.031,0:17:02.041
covering today of the concept

0:17:02.041,0:17:05.032
and the diving into it with your simon[br]in small groups are really where the

0:17:05.032,0:17:06.066
learnings going to happen

0:17:06.066,0:17:08.999
but by the end of this series of[br]sessions

0:17:08.999,0:17:10.006
you should be able to do some

0:17:10.006,0:17:12.016
fairly basic diagnostic

0:17:12.016,0:17:14.022
diagnostic question formulation

0:17:14.022,0:17:17.339
you should be able to define and uh...[br]calculate

0:17:17.339,0:17:20.959
sensitivity specificities and the[br]predicted values for different

0:17:20.959,0:17:24.065
diagnostic test for an introduce that[br]concept you today and tomorrow

0:17:24.065,0:17:27.048
and you should be able to explain how[br]risk factor

0:17:27.048,0:17:30.289
that god can thrive prior probabilities

0:17:30.289,0:17:33.669
and how this concept relates to[br]prevalence

0:17:33.669,0:17:37.749
and then finally you should be able to[br]modify probabilities from test results

0:17:37.749,0:17:39.007
through on number of different[br]mechanisms

0:17:39.007,0:17:44.009
we introduce you to the concept obeys[br]probabilistic reasoning as a way of

0:17:44.009,0:17:46.043
modifying probabilities over time

0:17:46.043,0:17:47.059
today we're gonna use

0:17:47.059,0:17:51.045
to buy two tables which is a of more[br]straightforward

0:17:51.045,0:17:55.027
easy to conceptualize and visualize way[br]of modifying probabilities

0:17:55.027,0:17:58.429
but you'll get more and more practice[br]with using that keep in mind that it is

0:17:58.429,0:18:03.013
just as good as base so these are[br]presented to you as you should be one

0:18:03.013,0:18:07.049
over the other represented the u<u>s</u>[br]items to put in your toolbox in portland

0:18:07.049,0:18:07.057
out

0:18:07.057,0:18:09.909
at different points when the need arises

0:18:09.909,0:18:13.038
there also other tools that are[br]available that will introduce to you one

0:18:13.038,0:18:14.094
called likelihood ratios

0:18:14.094,0:18:16.081
and you'll get a chance to practice[br]these

0:18:16.081,0:18:20.029
in your assignments and in your smokers

0:18:20.029,0:18:24.072
so just like we had the odyssey as a[br]case for introducing you to use

0:18:24.072,0:18:29.013
probabilistic reasoning this time really[br]immerse yourself in a clinical case and

0:18:29.013,0:18:31.075
i want you to think about this again[br]just with uh...

0:18:31.075,0:18:35.083
limited amount of knowledge you have[br]about this condition of this disease

0:18:35.083,0:18:37.033
whatever you have this fall

0:18:37.033,0:18:40.057
but bring to bear your experience as we[br]work through this case during the

0:18:40.057,0:18:42.009
remaining a bit the remainder of this[br]like

0:18:42.009,0:18:45.044
so the cases is sixty year old man

0:18:45.044,0:18:47.059
who does not have heart disease

0:18:47.059,0:18:50.799
who presents with sudden onset of[br]shortness of breath

0:18:50.799,0:18:53.002
dismissed is a term that we use

0:18:53.002,0:18:56.099
so here is a politically description of[br]the problem that you can see

0:18:56.099,0:19:00.008
yesterday after he flew in from[br]california the day before

0:19:00.008,0:19:03.091
he'll blokes suddenly in the middle of[br]the night at three in the morning with

0:19:03.091,0:19:05.092
sudden shortness of breath

0:19:05.092,0:19:08.089
so we woke up gasping for air at three[br]in the morning

0:19:08.089,0:19:10.014
and he tells you

0:19:10.014,0:19:12.057
that you ask them one question which is

0:19:12.057,0:19:16.082
well was it bad when you were lying down[br]and that's why you setup or was it worth

0:19:16.082,0:19:19.066
when you or is it about the same[br]regardless of whether you're setting up

0:19:19.066,0:19:20.009
ur lying down

0:19:20.009,0:19:24.097
because the people maybe was worse than[br]usual you said you know what

0:19:24.097,0:19:26.007
actually is it

0:19:26.007,0:19:28.082
any different online down if i'm sitting[br]up

0:19:28.082,0:19:30.003
i'm still

0:19:30.003,0:19:33.037
feeling short of breath and it won't be[br]up in the middle of the night

0:19:33.037,0:19:36.022
all right so that is your initial chief[br]complaint

0:19:36.022,0:19:40.023
this is something that you'll get used[br]to uh... as you do your data uh...

0:19:40.023,0:19:43.059
queries from uh... from patients at your[br]data gathering

0:19:43.059,0:19:44.051
from from different

0:19:44.051,0:19:46.046
but you being a good clinician

0:19:46.046,0:19:49.088
you start asking some follow-up[br]questions just like a good clinician

0:19:49.088,0:19:53.022
uh... or good mccain sort of building on[br]the mechanic model that we introduce you

0:19:53.022,0:19:54.052
to a week ago

0:19:54.052,0:19:58.001
so you ask him what other symptoms were[br]you feeling at the time

0:19:58.001,0:20:02.008
now as you get more sophisticated you[br]will be asking more specific questions

0:20:02.008,0:20:02.085
right now

0:20:02.085,0:20:05.019
sort of the about what i would expect

0:20:05.019,0:20:08.025
and what seems to be able to do what[br]else we feeling at the time

0:20:08.025,0:20:10.084
well he says does not testing

0:20:10.084,0:20:15.399
he doesn't have a leg pain he doesn't[br]notice any swelling of his leg

0:20:15.399,0:20:18.899
he says idea just come back from a long[br]plane ride he flew in from california

0:20:18.899,0:20:21.067
solicit was about five hours

0:20:21.067,0:20:23.074
nonstop

0:20:23.074,0:20:27.066
and he's had no problems like this[br]before that he knows

0:20:27.066,0:20:29.094
this shortness of breath

0:20:29.094,0:20:34.001
he takes one aspirin every day and he[br]does a smoke a pack of cigarettes

0:20:34.001,0:20:35.067
everyday

0:20:35.067,0:20:38.669
so that's kind of the next phase of[br]diagnostic

0:20:38.669,0:20:41.017
intake

0:20:41.017,0:20:45.014
so the question that faces all of us[br]just like the mechanic faces

0:20:45.014,0:20:48.007
is to be able to build a differential[br]diagnosis you remember me mentioning

0:20:48.007,0:20:50.009
well we as clinicians

0:20:50.009,0:20:52.045
still differential diagnoses all the[br]time

0:20:52.045,0:20:55.059
and basically differential diagnosis is[br]a list

0:20:55.059,0:20:59.929
of possibilities with associated likely[br]that's with associated probabilities

0:20:59.929,0:21:04.047
so as we mentioned last time if you can[br]p of a particular condition you'd be

0:21:04.047,0:21:06.006
saying that the likelihood that

0:21:06.006,0:21:09.001
this particular condition is the reason[br]for the shortness of breath

0:21:09.001,0:21:11.098
is x percent that's how you would write[br]that down

0:21:11.098,0:21:16.169
and what you would do is you place it in[br]descending order of likelihood and you

0:21:16.169,0:21:18.003
would be talking about wine

0:21:18.003,0:21:20.059
if you could get this

0:21:20.059,0:21:21.799
conceptual approach

0:21:21.799,0:21:24.049
jupe all your differential diagnoses

0:21:24.049,0:21:27.036
you will do well in medicine because[br]this is how we talk

0:21:27.036,0:21:31.046
now we don't do it necessarily in such[br]mathematical discrete models

0:21:31.046,0:21:34.076
is exactly what we talk when we talk[br]with another position we like you know

0:21:34.076,0:21:35.013
what

0:21:35.013,0:21:39.169
i think this patient has colon cancer[br]it's definitely more likely that he's

0:21:39.169,0:21:41.037
got colon cancer than he has hemorrhoids

0:21:41.037,0:21:44.049
that's kind of how we speak in barely in[br]formal settings

0:21:44.049,0:21:45.659
when we're discussing

0:21:45.659,0:21:48.074
uh... the case uh... a particular[br]patients case in trying to understand it

0:21:48.074,0:21:49.063
yala g

0:21:49.063,0:21:52.046
what we're really doing though is that[br]words generating a differential

0:21:52.046,0:21:56.032
diagnosis and it is the regardless of[br]what field you're going to do

0:21:56.032,0:21:58.059
you'll be doing this over and over again

0:21:58.059,0:22:01.006
so you get to your first one today

0:22:01.006,0:22:02.008
so now what i'd like you to do

0:22:02.008,0:22:04.004
is think about

0:22:04.004,0:22:08.006
what possibilities may be going on with[br]this particular time

0:22:08.006,0:22:12.088
talk it over with your partner list two[br]or three things that might be going on

0:22:12.088,0:22:18.023
and i will talk about what i think might[br]be going on

0:22:18.023,0:23:17.009
e

0:23:17.009,0:23:21.064
okay productive well on the five because[br]it's probably arctic every different

0:23:21.064,0:23:22.059
about yourself

0:23:22.059,0:23:24.011
at this stage that you're at

0:23:24.011,0:23:25.091
but it's not wrong to try

0:23:25.091,0:23:28.007
so let's just hear something you don't[br]have to give me a probability or

0:23:28.007,0:23:29.049
anything like that

0:23:29.049,0:23:38.098
just give me some possibilities of what[br]might be going on

0:23:38.098,0:23:42.034
all materialism versus congestive heart[br]failure okay so we've got pulmonary

0:23:42.034,0:23:43.219
embolism

0:23:43.219,0:23:45.679
congestive heart failure what else do we[br]go

0:23:45.679,0:23:50.098
sleep apnea okay great other things yeah

0:23:50.098,0:23:54.026
guilty gear emphysema while you guys and[br]he you've gone through medical school

0:23:54.026,0:23:57.074
before these are great coverage is a[br]great differential diagnosis absolutely

0:23:57.074,0:24:01.269
ep

0:24:01.269,0:24:03.087
events

0:24:03.087,0:24:07.083
hotbed i'd i didn't ask him about scuba[br]diving and whether he had uh...

0:24:07.083,0:24:10.038
at whether he had done that but[br]certainly that would be a follow-up

0:24:10.038,0:24:12.055
question that we would act

0:24:12.055,0:24:15.027
these are these are great things now[br]let's peace apart with these things me

0:24:15.027,0:24:17.063
first of all what is a pulmonary[br]embolism

0:24:17.063,0:24:20.017
which had pulmonary embolism you know[br]what it p<u>s</u>

0:24:20.017,0:24:40.009
unexplained

0:24:40.009,0:24:41.094
so o'clock in the long

0:24:41.094,0:24:45.099
the person was sitting in mobile for a[br]period of time which allows rumbled sis

0:24:45.099,0:24:50.029
to develop especially in the lower[br]extremities which can then migrate up

0:24:50.029,0:24:51.088
and gets stuck in the long

0:24:51.088,0:24:55.059
you stated that his shortness of breath[br]with sudden and so you started unpack

0:24:55.059,0:24:58.027
the whole concept of rationale and my[br]thinking that

0:24:58.027,0:25:01.023
versus some of the other things because[br]often times when you get a p<u>e</u> it

0:25:01.023,0:25:04.087
suddenly breaks off part of your of the[br]clock suddenly breaks off and goes into

0:25:04.087,0:25:06.022
the pulmonary basketball

0:25:06.022,0:25:09.389
now you'll understate you'll start[br]developing the language around that but

0:25:09.389,0:25:13.049
that's a great way to explain that you[br]also mentioned congestive heart failure

0:25:13.049,0:25:15.679
now what is congestive heart

0:25:15.679,0:25:18.041
art which on the spot but i was a good[br]differential i'm coming back into our

0:25:18.041,0:25:42.015
world seven you know

0:25:42.015,0:25:46.069
all right so congestive heart failure[br]being basically eight at in enhanced

0:25:46.069,0:25:49.014
pulmonary vascular

0:25:49.014,0:25:51.047
in the palm area vascular system because

0:25:51.047,0:25:53.081
the heart is not able to

0:25:53.081,0:25:58.051
nearly as good injection of the blood[br]through the periphery and so things back

0:25:58.051,0:26:01.159
up for a bride of the reasons either[br]though

0:26:01.159,0:26:04.003
orgasm pump is well it's two-step you[br]got valvular leakage

0:26:04.003,0:26:07.095
and it backs up into the pulmonary[br]vasculature you increase the pressure it

0:26:07.095,0:26:12.053
you cause pulmonary edema which gives[br]you offensive shortness of breath but as

0:26:12.053,0:26:15.091
you mentioned oftentimes that'll be[br]accompanied by peripheral oedema because

0:26:15.091,0:26:19.001
of the heart backs up from left[br]ventricular failure right ventricular

0:26:19.001,0:26:19.083
failure

0:26:19.083,0:26:20.093
than you actually have

0:26:20.093,0:26:22.669
summit denying your lower extremities

0:26:22.669,0:26:26.046
she doesn't according to him we haven't[br]done the examination you so that's the

0:26:26.046,0:26:30.012
caveat here but that may be a reasonable[br]thing to come up with uh... to uh... to

0:26:30.012,0:26:33.679
come up with in your differential and[br]you put it lower because there were some

0:26:33.679,0:26:35.909
aspects that weren't necessarily as

0:26:35.909,0:26:38.059
consistent with that bag no's' right

0:26:38.059,0:26:41.033
so that's a that's a great way to[br]approach the differential

0:26:41.033,0:26:43.001
i would mention obstructive sleep apnea

0:26:43.001,0:26:43.929
overhear yet

0:26:43.929,0:26:46.073
what's obstructive sleep apnea might[br]like that that here

0:26:46.073,0:26:57.809
e

0:26:57.809,0:27:00.085
pacbell now that site so what let me[br]just uh... unpack what you're saying

0:27:00.085,0:27:01.449
there

0:27:01.449,0:27:04.049
you're commenting on the fact that this[br]guy woke up in the middle of the night

0:27:04.049,0:27:06.086
with shortness of breath now oftentimes[br]people who

0:27:06.086,0:27:09.059
have obstructive sleep apnea don't[br]actually wake up

0:27:09.059,0:27:12.027
but they have apnea episodes which means[br]that they

0:27:12.027,0:27:13.429
stopped breathing

0:27:13.429,0:27:17.036
for a period of time and sometimes i can[br]cause them to suddenly startle and wake

0:27:17.036,0:27:20.005
up they don't necessarily wake up short[br]of breath but they can't

0:27:20.005,0:27:23.065
absolutely until anyone that wakes up in[br]the middle of the night

0:27:23.065,0:27:25.063
i'm certainly thinking about sleep apnea

0:27:25.063,0:27:29.369
it's probably one of the most under[br]diagnosed conditions in this country

0:27:29.369,0:27:32.769
i didn't know the reggie white died of[br]it but he certainly would be pat rescue

0:27:32.769,0:27:34.839
uvic because people who have are

0:27:34.839,0:27:37.048
uh... and i don't know how it will be c[br]was but large

0:27:37.048,0:27:41.059
body habit is certainly is a risk factor[br]for obstructive sleep apnea

0:27:41.059,0:27:45.429
also can lead to right sided congestive[br]heart failure so might also be connected

0:27:45.429,0:27:47.065
to one of the diagnoses that we heard[br]early on

0:27:47.065,0:27:52.005
so keep in mind that sometimes diagnoses[br]are completely independent of themselves

0:27:52.005,0:27:55.009
revelry talked about independent[br]independent events

0:27:55.009,0:27:58.299
sometimes different items in your[br]differential are actually related to

0:27:58.299,0:28:02.002
other items that you differential so we[br]have to keep that in mind as well

0:28:02.002,0:28:05.009
by legal said feel p<u>d</u> in the back and[br]now possible emphysema what is that

0:28:05.009,0:28:07.078
and why might he be at risk for them

0:28:07.078,0:28:28.659
front his

0:28:28.659,0:28:29.094
baton so

0:28:29.094,0:28:32.098
clearly he's got to look just to[br]reiterate what you're saying

0:28:32.098,0:28:34.088
he's a smoker

0:28:34.088,0:28:39.029
long-term smoking can cause destruction[br]and inflammation to the pulmonary

0:28:39.029,0:28:40.008
bronchus tree

0:28:40.008,0:28:42.029
andy alveolar

0:28:42.029,0:28:45.026
uh... components of it what you learn[br]about this year and next year

0:28:45.026,0:28:49.000
uh... destruction of the albee ally is[br]typically what we see as a mechanism

0:28:49.000,0:28:50.038
towards emphysema

0:28:50.038,0:28:55.049
which is one manifestation clinical[br]manifestation of seo p<u>d</u> and certainly

0:28:55.049,0:28:56.065
can impair oxygen

0:28:56.065,0:28:59.075
exchange which would make you short of[br]breath and destiny

0:28:59.075,0:29:03.034
and maybe he's in the early stages maybe[br]this is just his first manifestation of

0:29:03.034,0:29:03.799
that

0:29:03.799,0:29:06.015
you know he said he has ended for breath[br]before

0:29:06.015,0:29:09.033
but your focusing on his rest

0:29:09.033,0:29:10.077
dot keep that in mind

0:29:10.077,0:29:14.041
some people were focusing on how he[br]presented waking up in the middle of the

0:29:14.041,0:29:15.029
night

0:29:15.029,0:29:17.085
some people are focusing on risk

0:29:17.085,0:29:21.004
both are absolutely critical as you get[br]as you generate your differential

0:29:21.004,0:29:21.099
diagnosis

0:29:21.099,0:29:22.075
risk

0:29:22.075,0:29:27.001
drives the order often of the things in[br]your differential diagnosis

0:29:27.001,0:29:28.559
but how u manifest

0:29:28.559,0:29:31.007
also changes the order and what you're[br]thinking about

0:29:31.007,0:29:33.035
in a different likeness

0:29:33.035,0:29:35.073
both of the things that we need to walk[br]in with

0:29:35.073,0:29:39.052
and as we think about observational[br]studies tying this to what doctor grover

0:29:39.052,0:29:41.016
was talking about last week

0:29:41.016,0:29:44.929
observation als studies give us[br]information about race

0:29:44.929,0:29:47.027
they give us information about risk[br]factor

0:29:47.027,0:29:50.008
that contribute to different clinical[br]case uh... disorders

0:29:50.008,0:29:53.429
so very important to trying title of[br]this to get and question over here some

0:29:53.429,0:29:56.072
yes

0:29:56.072,0:30:00.042
back g<u>o</u>p_ d is chronic obstructive[br]pulmonary disease

0:30:00.042,0:30:04.024
it is the long-term manifestations of[br]tobacco use

0:30:04.024,0:30:07.057
it can manifest through either emphysema[br]where you have destruction of the

0:30:07.057,0:30:08.083
alveolar tissue

0:30:08.083,0:30:11.003
and impaired oxygen exchange as a result

0:30:11.003,0:30:14.179
you can also manifest as what we call[br]chronic bronchitis where you have a

0:30:14.179,0:30:16.000
tremendous amount of inflammation

0:30:16.000,0:30:20.047
in the broncos and with mucus production[br]which can also cause impaired oxygen

0:30:20.047,0:30:21.034
i mean

0:30:21.034,0:30:22.097
uh... oxygenation

0:30:22.097,0:30:25.149
so sorry i didn't identified annual

0:30:25.149,0:30:28.559
learn all of these concepts as you move[br]on

0:30:28.559,0:30:31.075
so you're doing a great job building[br]your first differential diagnosis now

0:30:31.075,0:30:33.045
the problem is is i also said

0:30:33.045,0:30:36.085
we have to start assigning probabilities[br]to get to these different

0:30:36.085,0:30:40.013
uh... clinical manifestations of just[br]give you an idea of what my list was

0:30:40.013,0:30:41.076
before we get started

0:30:41.076,0:30:43.072
that's right

0:30:43.072,0:30:45.013
congestive heart failure

0:30:45.013,0:30:47.059
and that the amount exacerbate shin

0:30:47.059,0:30:49.092
and i also thought about asthma which[br]could be another

0:30:49.092,0:30:53.269
different manifestation that is not[br]necessarily smoking related

0:30:53.269,0:30:56.749
but also uh... can contribute to airway[br]inflammation

0:30:56.749,0:30:59.969
i didn't have obstructive sleep apnea in[br]my differential that doesn't mean that

0:30:59.969,0:31:01.589
it's wrong to put it there

0:31:01.589,0:31:05.249
um... many people would and what you'll[br]find is a different clinicians will

0:31:05.249,0:31:09.419
bring their different behind the scenes[br]to their differential diagnosis

0:31:09.419,0:31:12.002
of the question is what do you do when[br]they're all these behind seas out there

0:31:12.002,0:31:17.065
and how do we assign probabilities to[br]the different uh... clinical

0:31:17.065,0:31:19.549
uh... entities in your differential

0:31:19.549,0:31:22.789
or sometimes we can do it by a gut[br]feeling

0:31:22.789,0:31:26.098
based on what we know about the disease[br]based on what we know about the patient

0:31:26.098,0:31:29.279
based on what we know about the for[br]respects

0:31:29.279,0:31:32.071
and so here's my gut feeling[br]differential diagnosis

0:31:32.071,0:31:34.096
i put p<u>e</u> at the top

0:31:34.096,0:31:36.659
i could see a jeff next

0:31:36.659,0:31:40.011
at thirty uh... and i put emphysema[br]thirteen asthma fourth

0:31:40.011,0:31:43.016
and i tried to make it all add up to a[br]hundred percent so it was nice to meet

0:31:43.016,0:31:46.539
so i could forty thirty twenty ten

0:31:46.539,0:31:49.046
there is at a right answer you don't[br]know

0:31:49.046,0:31:53.024
that's just my gut feeling but what it[br]does tell you is i didn't think that

0:31:53.024,0:31:57.909
pete was so overwhelmingly likely and i[br]would put that at seventy percent and

0:31:57.909,0:31:59.036
everything else down at the bottom

0:31:59.036,0:32:02.006
there may be clinical conditions where[br]you do that but keep in mind that each

0:32:02.006,0:32:04.007
one of these diagnosis

0:32:04.007,0:32:05.068
had both its

0:32:05.068,0:32:08.038
can uh... consistent features

0:32:08.038,0:32:11.058
and something that we're just kind of[br]atypical

0:32:11.058,0:32:14.075
why wouldn't it be a p<u>e</u> well he said[br]he didn't have a new leads well he'll

0:32:14.075,0:32:18.007
appear on a plane ride for five hours[br]most people don't get a d<u>d</u>t_

0:32:18.007,0:32:19.499
well maybe ever

0:32:19.499,0:32:20.092
symbol that looks like

0:32:20.092,0:32:23.309
y c h f not bad

0:32:23.309,0:32:25.054
because there's you know there's some[br]things that are consistent with a but he

0:32:25.054,0:32:27.045
doesn't have flirts from any of you

0:32:27.045,0:32:29.075
until their fingers that will sort of[br]make you head

0:32:29.075,0:32:31.092
and these numbers are part of making

0:32:31.092,0:32:34.539
are are my manifestation of making

0:32:34.539,0:32:37.669
uh... contribute communicating the head

0:32:37.669,0:32:40.012
there a couple of other things you can[br]do with this

0:32:40.012,0:32:42.007
so for example remember

0:32:42.007,0:32:44.096
you can combine probabilities of[br]different events

0:32:44.096,0:32:49.024
so what is the probability that[br]shortness of breath is due to be there p

0:32:49.024,0:32:51.009
foresee a chap

0:32:51.009,0:32:55.094
given these a particular numbers when[br]you guys think

0:32:55.094,0:33:02.149
seventy percent

0:33:02.149,0:33:05.669
if the two are mutually independent[br]events

0:33:05.669,0:33:08.046
meaning that they're not dependent on[br]each other not meaning that if you happy

0:33:08.046,0:33:10.659
you are not more likely to get seja

0:33:10.659,0:33:11.061
or vice versa

0:33:11.061,0:33:14.018
because if there is that overlap remote[br]from what we understand about the

0:33:14.018,0:33:17.058
disease and you can't combine them by[br]adding so yes the answer to that would

0:33:17.058,0:33:21.038
be seventy percent but remember a thing[br]in mind that provided that both don't

0:33:21.038,0:33:22.098
happen simultaneously

0:33:22.098,0:33:26.002
just as an intellectual exercise if you[br]thought that there might be a ten

0:33:26.002,0:33:27.062
percent overlap

0:33:27.062,0:33:32.088
in the likelihood that you have both p n[br]c h f bowing out of the same time

0:33:32.088,0:33:35.012
meaning that they are dependent and then[br]sport

0:33:35.012,0:33:36.619
that they're both likely

0:33:36.619,0:33:39.389
uh... the it's possible that you're[br]having both of them happen at the same

0:33:39.389,0:33:43.002
time then that you could combine the two[br]by saying what is the likelihood that

0:33:43.002,0:33:45.088
you have either p or c h f

0:33:45.088,0:33:47.045
but it wouldn't be seventy percent

0:33:47.045,0:33:50.071
would actually be sixty percent because[br]there's also ten percent chance

0:33:50.071,0:33:53.004
but both are happy happening[br]simultaneously

0:33:53.004,0:33:56.059
but the good intellectual exercise to go[br]through again the numbers art as

0:33:56.059,0:33:59.399
important as the concept that it goes[br]down

0:33:59.399,0:34:01.005
when but to events for depend

0:34:01.005,0:34:03.017
keep in mind that in medicine

0:34:03.017,0:34:05.096
their are absolutely independent events

0:34:05.096,0:34:08.129
and their absolutely

0:34:08.129,0:34:11.909
that will be dependent and has you go[br]through your blocks and understand the

0:34:11.909,0:34:13.789
diseases you'll get an appreciation

0:34:13.789,0:34:18.799
berwyn things are determined and when[br]they read

0:34:18.799,0:34:21.095
so basically what we're doing is worth[br]actually creating

0:34:21.095,0:34:23.659
prior probability

0:34:23.659,0:34:27.469
before we have done any further down the[br]track gathering with this patient

0:34:27.469,0:34:29.061
re-affirm a couple of questions that we[br]would ask

0:34:29.061,0:34:33.005
well before we do any further exit we[br]can do the physical exam yet

0:34:33.005,0:34:36.031
we didn't do any real specific[br]questioning within the week testing yet

0:34:36.031,0:34:37.369
we're generating

0:34:37.369,0:34:41.279
it prior probability remember we did[br]that with the woman with the b<u>r</u>c_ a

0:34:41.279,0:34:43.099
haitian that we were concerned about

0:34:43.099,0:34:45.729
we had a prior probability with her[br]walking in

0:34:45.729,0:34:47.369
do when she was twenty years old

0:34:47.369,0:34:50.002
well this is a prior probability that's[br]based on a number of different factors

0:34:50.002,0:34:52.789
that i doubt that i mentioned

0:34:52.789,0:34:56.013
on the other hand you can actually[br]generated prior probability

0:34:56.013,0:35:00.034
using some tools that are out there is[br]what don't want to demonstrate obscene

0:35:00.034,0:35:03.669
as some of the tools that might be[br]helpful to you

0:35:03.669,0:35:07.082
so why is there are these things called[br]clinical prediction rules

0:35:07.082,0:35:12.009
mechanical production rules are ways of[br]using the literature and what we know

0:35:12.009,0:35:15.026
about the literature estimate s

0:35:15.026,0:35:17.659
about particular disease

0:35:17.659,0:35:18.709
and

0:35:18.709,0:35:23.119
the uh... the way that we did there are[br]a number of them that are out there

0:35:23.119,0:35:26.969
pulmonary embolism is one of those[br]clinical diseases that actually has a

0:35:26.969,0:35:29.579
number of different political[br]predictions and i want to sort of show

0:35:29.579,0:35:30.028
you

0:35:30.028,0:35:33.269
what uh... what one uh... looks like

0:35:33.269,0:35:36.839
so what you have here to really think[br]that your slides that you can use as

0:35:36.839,0:35:37.043
well

0:35:37.043,0:35:39.599
this is mad calc three counts

0:35:39.599,0:35:42.959
this is on the uh... you guys have[br]access to this and uh... they're unknown

0:35:42.959,0:35:44.002
bura different uh...

0:35:44.002,0:35:47.239
their number of different medical[br]calculators here

0:35:47.239,0:35:50.092
for p what you would do is you would[br]enter in the day the for the particular

0:35:50.092,0:35:51.889
patient

0:35:51.889,0:35:57.409
and then it would give you step here in[br]the lower right hand corner cc

0:35:57.409,0:36:00.769
so let's do that for this particular[br]case

0:36:00.769,0:36:02.649
based on what we know right now

0:36:02.649,0:36:07.579
based on what we were going out the[br]sixties right so we put the sixties

0:36:07.579,0:36:09.013
we also know that he's made

0:36:09.013,0:36:10.609
so we put that

0:36:10.609,0:36:14.389
and then you'll see a whole series of[br]risk factors here

0:36:14.389,0:36:18.819
let's say we don't deal with uh... let's[br]go down and see what he has

0:36:18.819,0:36:22.589
we know he's got the acute onset which[br]means some that's another

0:36:22.589,0:36:23.068
word that you learn

0:36:23.068,0:36:25.579
sudden onset of this issue

0:36:25.579,0:36:26.759
we click on that

0:36:26.759,0:36:30.399
notice what's happening to the risk as[br]we go through this

0:36:30.399,0:36:33.889
just being sixty years old and mail

0:36:33.889,0:36:36.649
and then adding acute onset of dyspnea

0:36:36.649,0:36:39.749
this risk number goes up to fifty[br]percent

0:36:39.749,0:36:42.329
really jumps up there

0:36:42.329,0:36:46.023
and if we added that he might have been[br]immobilized with saying this

0:36:46.023,0:36:47.659
let's say he sat

0:36:47.659,0:36:48.073
in a plane

0:36:48.073,0:36:52.229
completely comatose for five hours[br]didn't move out what

0:36:52.229,0:36:56.419
that would probably qualify as[br]immobilization

0:36:56.419,0:36:58.259
let's say we clicked that

0:36:58.259,0:37:02.079
you'll see that his risk of having a[br]p<u>e</u> with all of this

0:37:02.079,0:37:04.279
is now sixty percent

0:37:04.279,0:37:07.249
so my gut feeling of forty percent

0:37:07.249,0:37:11.839
probably and underestimation now this is[br]a gut feeling this is based on

0:37:11.839,0:37:15.069
spa operational stocks that are out[br]there and putting them into a

0:37:15.069,0:37:16.509
mathematical model

0:37:16.509,0:37:19.006
you can get these things for your[br]handheld device

0:37:19.006,0:37:21.097
you can put them on the web a lot of[br]these are being integrated into the

0:37:21.097,0:37:24.005
electronic health record for positions

0:37:24.005,0:37:24.989
so that these

0:37:24.989,0:37:28.189
guides can be placed right at the point[br]of care

0:37:28.189,0:37:31.319
i'd encourage you to think about these[br]and try to explore some of these because

0:37:31.319,0:37:34.046
they were a number of these for a number[br]of different conditions out there

0:37:34.046,0:37:37.047
but we're gonna return to this as we go[br]through so right now

0:37:37.047,0:37:39.096
we're starting around sixty percent

0:37:39.096,0:37:42.049
as our prior probability

0:37:42.049,0:37:44.094
but you realize also that there's a[br]number of questions here that we just

0:37:44.094,0:37:48.749
don't know the answer to the right legal[br]fees at a fever we don't know we know

0:37:48.749,0:37:51.014
that he doesn't have a history very[br]vascular disease

0:37:51.014,0:37:54.045
we don't know if he passed out we don't[br]know if he's actually got one-sided

0:37:54.045,0:37:55.049
lights while

0:37:55.049,0:37:57.869
so there's more data we need to get

0:37:57.869,0:37:59.539
so let's gather

0:37:59.539,0:38:05.169
so more date

0:38:05.169,0:38:08.059
so here's some more information then i'm[br]gonna throw at you based on this

0:38:08.059,0:38:09.619
particular case

0:38:09.619,0:38:13.169
you talk about family history find out[br]that he actually

0:38:13.169,0:38:14.599
has had

0:38:14.599,0:38:19.149
he has a family that is that the d<u>d</u>t_[br]in the past

0:38:19.149,0:38:22.699
pretty for it

0:38:22.699,0:38:26.063
you do a physical exam on him and you[br]find a his blood oxygen saturation is

0:38:26.063,0:38:28.109
normal on room air

0:38:28.109,0:38:30.989
so these oxygen eighty five

0:38:30.989,0:38:35.359
checkers respiratory rate at sixteen[br]that's generally that's a little fast

0:38:35.359,0:38:37.099
but it's probably okay but

0:38:37.099,0:38:39.017
his pulse rate is a hundred and buy it[br]now

0:38:39.017,0:38:43.839
united now that a hundred five ezell[br]elevate we would call that eka kartik

0:38:43.839,0:38:45.739
so he's technopark

0:38:45.739,0:38:49.005
and you examine his loans as you will[br]learn to do this year and you'll find

0:38:49.005,0:38:52.949
when you became his patients' lungs that[br]he has crackles

0:38:52.949,0:38:54.539
n<u>t</u>s<u>b</u>'s

0:38:54.539,0:38:56.339
user crackles are sort of

0:38:56.339,0:38:57.053
they sound like crackers

0:38:57.053,0:38:59.489
we've ever listen to rice crispy

0:38:59.489,0:39:02.859
that's what it sounds like a bit sounds[br]with inspiration you would get crap that

0:39:02.859,0:39:06.429
usually indicates that there's some[br]degree of a team up in the long some

0:39:06.429,0:39:10.007
degree of swelling in the long and as[br]the albee a liar trying to expand

0:39:10.007,0:39:12.949
they pop open up a very easy way but[br]enough

0:39:12.949,0:39:15.089
tough way because there's a lot of[br]surface tension at each of you

0:39:15.089,0:39:19.119
level because of the fluid in the[br]interstitial space

0:39:19.119,0:39:23.649
he's also got leases leases are[br]indications of airway obstruction small

0:39:23.649,0:39:26.189
airways obstruction in the long

0:39:26.189,0:39:29.095
but you'll also notice he doesn't have a[br]problem which means that he doesn't have

0:39:29.095,0:39:33.339
this sort of uh... inflammation in the[br]pleural space which will learn about

0:39:33.339,0:39:36.015
and he doesn't have evidence of[br]consolidation consolidation would give

0:39:36.015,0:39:39.039
you some clues that he might have an emo

0:39:39.039,0:39:41.589
we don't have either of those

0:39:41.589,0:39:44.449
but you also examine is like and you[br]find that even though he didn't think it

0:39:44.449,0:39:47.569
was a swollen it absolutely is well

0:39:47.569,0:39:49.869
and you feel of any

0:39:49.869,0:39:50.081
below his knee

0:39:50.081,0:39:54.002
most of the time we should be able to[br]feel the danes attorney but if they're

0:39:54.002,0:39:56.013
inflamed possibly because of a clock

0:39:56.013,0:39:58.439
you might feel below the knee

0:39:58.439,0:40:01.929
you get a chest x-ray that's normal

0:40:01.929,0:40:05.088
and you get the cagey in its shows that[br]his heart's going fast but nothing's

0:40:05.088,0:40:08.269
besides that

0:40:08.269,0:40:10.869
so now what we do is we go back

0:40:10.869,0:40:14.489
to the clinical prediction

0:40:14.489,0:40:17.094
calculator and cd about entering in this[br]data

0:40:17.094,0:40:22.169
so the additional data that will get

0:40:22.169,0:40:23.089
he not only is uh...

0:40:23.089,0:40:27.023
sixty years old and mailing it to keep[br]this thing out and let's say he's

0:40:27.023,0:40:29.169
immobilized he was a mobile as

0:40:29.169,0:40:34.999
we now find that he's gotten lateral[br]excellent

0:40:34.999,0:40:37.609
but that he also has leases

0:40:37.609,0:40:40.609
contracts

0:40:40.609,0:40:44.489
no notice what happens to pay attention[br]to the number as i enter the zip

0:40:44.489,0:40:48.038
i started out with sixty percent by[br]aditi lateral leg swelling what we're

0:40:48.038,0:40:50.589
getting really close for x seventy five[br]percent

0:40:50.589,0:40:52.719
but this person's that p

0:40:52.719,0:40:53.095
upholding a bit

0:40:53.095,0:40:57.059
remember we're talking about as long as[br]even though

0:40:57.059,0:40:58.499
the race

0:40:58.499,0:40:59.529
his lead

0:40:59.529,0:41:02.009
because if you've got to cut your leg[br]you're more likely to throw that but we

0:41:02.009,0:41:05.026
have a pulmonary embolism those two are[br]not

0:41:05.026,0:41:06.619
independent features

0:41:06.619,0:41:08.769
those who are dependent effects

0:41:08.769,0:41:12.269
so it dries it up to seven six percent[br]but knows what happened when i clicked

0:41:12.269,0:41:14.469
on visas and practice

0:41:14.469,0:41:18.269
that number within seventy five percent[br]of the thirty five percent

0:41:18.269,0:41:19.919
so what in your mind

0:41:19.919,0:41:21.839
must you be thinking

0:41:21.839,0:41:24.099
the presents of crackles and we use is[br]actually make

0:41:24.099,0:41:28.219
pulmonary embolism last like

0:41:28.219,0:41:32.559
in fact pulmonary embolism the number[br]one clinical finding in the long for p

0:41:32.559,0:41:33.729
is nothing

0:41:33.729,0:41:36.409
subtotal e normal pulmonary exam

0:41:36.409,0:41:38.889
just because you have a normal palm[br]trees and doesn't mean you don't have a

0:41:38.889,0:41:40.239
disease

0:41:40.239,0:41:42.066
as an important consideration but keep[br]in mind that this is a way of

0:41:42.066,0:41:43.058
quantifying

0:41:43.058,0:41:44.709
how much

0:41:44.709,0:41:49.013
dropped there is so we ever did all this[br]data and we're now at around thirty five

0:41:49.013,0:41:50.449
percent

0:41:50.449,0:41:52.319
so turns out i was about

0:41:52.319,0:42:06.169
or a percent was pretty close to thirty[br]five pst

0:42:06.169,0:42:10.047
there are interactional terms that are[br]built into the mathematical model here

0:42:10.047,0:42:13.579
so if you look above the rest

0:42:13.579,0:42:18.159
and sold those interactions are built[br]into how he calculates the factor some

0:42:18.159,0:42:20.809
which then translates to what the risks

0:42:20.809,0:42:23.093
so yes there are interaction terms[br]between these things

0:42:23.093,0:42:26.629
and it's calc it's all done in the[br]background

0:42:26.629,0:42:28.799
clinician you know i'm not gonna do that

0:42:28.799,0:42:31.669
and i'm certainly not to be able to look[br]at a study be able to know how to do

0:42:31.669,0:42:34.329
that that's why these calculators to be[br]very helpful

0:42:34.329,0:42:37.109
it'll give you an idea are we weigh off

0:42:37.109,0:42:39.719
or are we about right is this guy is

0:42:39.719,0:42:42.096
was my initial gut feeling over on[br]target yeah

0:42:42.096,0:42:45.839
was kind of on target even when we did[br]more data gathering

0:42:45.839,0:42:47.016
but you also get a sense

0:42:47.016,0:42:50.066
uh... why how different features[br]increase and decrease the likelihood

0:42:50.066,0:42:59.649
which is a good learning tool

0:42:59.649,0:43:02.689
rate

0:43:02.689,0:43:05.119
so the question is of why is

0:43:05.119,0:43:06.919
smoking and wake nodding here

0:43:06.919,0:43:10.529
the answer is is that smoking and wait[br]for actually not considered risk factors

0:43:10.529,0:43:12.679
for p

0:43:12.679,0:43:15.769
when they've looked at these studies[br]what you might think of boy there smoker

0:43:15.769,0:43:17.299
they're more likely to have a clock

0:43:17.299,0:43:19.059
into israel

0:43:19.059,0:43:21.269
just because you're a smoker doesn't[br]mean that you're more likely to have a

0:43:21.269,0:43:22.309
p<u>e</u>

0:43:22.309,0:43:25.039
now certain smokers do carry increase[br]from body chris

0:43:25.039,0:43:28.069
if you're a young woman who smoking on[br]or contraceptives

0:43:28.069,0:43:32.629
you already higher risk of developing a[br]lower extremity d<u>d</u>t_

0:43:32.629,0:43:33.819
at is clear

0:43:33.819,0:43:36.829
but that's not necessarily what we're[br]talking about here

0:43:36.829,0:43:39.879
over the lot big picture it doesn't[br]contribute risk

0:43:39.879,0:43:42.709
it also could be because the studies[br]were done but in this case is because

0:43:42.709,0:43:51.659
they're not respect

0:43:51.659,0:43:52.509
uh...

0:43:52.509,0:43:55.839
so here's the question if you are[br]thinking that there is a nother

0:43:55.839,0:43:59.599
possibility on your differential[br]diagnosis that is either equally or more

0:43:59.599,0:44:04.019
likely does it drive this down the[br]absentee answers absolutely it does

0:44:04.019,0:44:06.043
and there are limits to these clinical[br]prediction

0:44:06.043,0:44:09.052
so this is done in a vacuum their other[br]clinical prediction rules

0:44:09.052,0:44:13.031
where you can actually have a button[br]that says is an alternative diagnosis

0:44:13.031,0:44:17.549
equally or more likely when you do that[br]people drop your s

0:44:17.549,0:44:20.044
because it knows that there may be other[br]things going up this prediction will

0:44:20.044,0:44:25.029
didn't do that

0:44:25.029,0:44:29.045
station had a family history of a d<u>d</u>t_[br]but not a personal history dvd if you're

0:44:29.045,0:44:33.009
interested in what that would have done[br]you could do it if he had a dvd in the

0:44:33.009,0:44:34.269
past

0:44:34.269,0:44:38.539
it drives up from thirty five to fifty

0:44:38.539,0:44:41.979
yet family history of some of his family[br]with d

0:44:41.979,0:44:45.289
all these are great questions but the[br]most important thing to keep in mind is

0:44:45.289,0:44:48.299
you don't just have to go on gut feel

0:44:48.299,0:44:51.289
at these clinical prediction rules for[br]common diseases which are the ones that

0:44:51.289,0:44:51.097
are out there

0:44:51.097,0:44:53.074
can help you understand

0:44:53.074,0:44:58.249
the clinical manifestations of a[br]particular disease

0:44:58.249,0:45:00.859
so what does this have to do with what[br]we do

0:45:00.859,0:45:05.129
well keep in mind we're now

0:45:05.129,0:45:06.589
we are now at

0:45:06.589,0:45:09.089
um having completed our data gathering[br]things were based

0:45:09.089,0:45:12.058
with the prior probability of about[br]thirty five percent

0:45:12.058,0:45:14.949
at the station is happy

0:45:14.949,0:45:16.009
and so what we need to do you think[br]about

0:45:16.009,0:45:18.819
do we need to get a test

0:45:18.819,0:45:21.289
because the question that should be[br]going through your mind is the thirty

0:45:21.289,0:45:25.379
five percent high enough at allstate[br]yahoo dot abt and got a pulmonary

0:45:25.379,0:45:26.016
embolism

0:45:26.016,0:45:28.089
we're gonna treat you as such

0:45:28.089,0:45:31.149
hopefully thirty five percent is too low[br]for even you

0:45:31.149,0:45:34.529
to say boy i don't think that i would[br]point to treat based on that certainly

0:45:34.529,0:45:39.499
would be low for most of the nation's we[br]need to probably get some sort of text

0:45:39.499,0:45:44.489
so what this is a how those bridges over[br]into diagnostic test

0:45:44.489,0:45:47.489
so here is the question what we do with[br]this number

0:45:47.489,0:45:51.249
well if there was a test that existed[br]that could rule in pulmonary embolism as

0:45:51.249,0:45:52.022
the diagnosis

0:45:52.022,0:45:54.008
with a hundred percent sense certainty

0:45:54.008,0:46:00.529
we would be saying that probability of[br]this of a patient having a p

0:46:00.529,0:46:01.021
due to the

0:46:01.021,0:46:02.074
at the test is positive

0:46:02.074,0:46:05.619
is a hundred percent

0:46:05.619,0:46:09.269
and the question i would ask you is what[br]is the stressful

0:46:09.269,0:46:13.239
what we call this test the boot stain

0:46:13.239,0:46:18.289
the gold standard generally exist for[br]more most conditions where they're is

0:46:18.289,0:46:22.099
where works for the past week after the[br]finding of the best will stand at the

0:46:22.099,0:46:23.249
top

0:46:23.249,0:46:25.013
uh... it may not be the best test

0:46:25.013,0:46:26.036
that we can envision

0:46:26.036,0:46:27.069
but it's the best test

0:46:27.069,0:46:32.229
that is available

0:46:32.229,0:46:35.499
and the question that i would ask is if[br]you use the gold standard tests and you

0:46:35.499,0:46:37.859
found it

0:46:37.859,0:46:39.002
the test was positive

0:46:39.002,0:46:42.095
is the probability of an alternative[br]diagnosis remember that a test test

0:46:42.095,0:46:46.339
that's a gold standard is only the gold[br]standard or particular diagnosis

0:46:46.339,0:46:48.509
let's say there's another diagnosis

0:46:48.509,0:46:49.719
that you're interested in

0:46:49.719,0:46:50.869
is it zero

0:46:50.869,0:46:52.028
if the test is positive

0:46:52.028,0:46:53.043
the answer is no

0:46:53.043,0:46:54.279
because

0:46:54.279,0:46:56.043
sometimes you have two things going on

0:46:56.043,0:46:58.249
sometimes there are vents

0:46:58.249,0:47:00.999
that are related to each other dependent[br]on each other

0:47:00.999,0:47:02.071
for sometimes you just have bad luck

0:47:02.071,0:47:03.639
as a patient

0:47:03.639,0:47:06.619
and you have both pulmonary embolism and[br]c<u>h</u>a_

0:47:06.619,0:47:08.089
but the most important to keep thing to[br]keep in mind

0:47:08.089,0:47:12.279
is that we are always looking to see[br]what the gold standard is

0:47:12.279,0:47:16.459
but we can't always used to go see

0:47:16.459,0:47:19.789
so what is that not stick testing people[br]but not the testing

0:47:19.789,0:47:23.043
the the goal of diagnostic testing is to[br]help us modify probabilities

0:47:23.043,0:47:24.008
we talked about how

0:47:24.008,0:47:29.021
we modify probabilities based on history[br]taking physical exam other simple tests

0:47:29.021,0:47:32.015
complex s like the ones we're gonna talk[br]about

0:47:32.015,0:47:34.629
will help modify probabilities as well

0:47:34.629,0:47:36.129
but they cost a lot of money

0:47:36.129,0:47:39.016
and so we need to approach argues a[br]diagnostic tests

0:47:39.016,0:47:42.269
judicious

0:47:42.269,0:47:45.069
so in order to understand what we're[br]looking for work in a study about

0:47:45.069,0:47:48.119
diagnostic test we need to understand

0:47:48.119,0:47:53.999
how people related items to test

0:47:53.999,0:47:56.049
really does relate instead of

0:47:56.049,0:47:57.549
the patient

0:47:57.549,0:47:59.092
uh... population were interested in

0:47:59.092,0:48:02.049
what we're really trying to use the[br]following

0:48:02.049,0:48:05.169
a disease state

0:48:05.169,0:48:07.799
what is the disease that we're trying to[br]diagnose

0:48:07.799,0:48:11.109
in this particular case if ur interested[br]in another test to use

0:48:11.109,0:48:14.389
it would be the disease state would be a[br]pulmonary embolism

0:48:14.389,0:48:15.579
intervention

0:48:15.579,0:48:19.809
would actually be the test itself so[br]what tester we interested in his room

0:48:19.809,0:48:22.279
looking through the literature

0:48:22.279,0:48:25.999
the comparison group is not another[br]therapy but it was in the therapeutic

0:48:25.999,0:48:26.077
questions

0:48:26.077,0:48:28.749
it's the gold standard

0:48:28.749,0:48:30.049
so you're trying to compare

0:48:30.049,0:48:32.099
a test of interest

0:48:32.099,0:48:34.839
against what is the best test that's out[br]there

0:48:34.839,0:48:37.459
the problem with the best test that's[br]out there is that it's frequently

0:48:37.459,0:48:38.032
infeasible

0:48:38.032,0:48:41.032
sometimes dangerous even though it's the[br]best s so we're looking for an

0:48:41.032,0:48:44.054
alternative test that we can use i can[br]help us with our page so that those

0:48:44.054,0:48:46.279
favoritism

0:48:46.279,0:48:49.879
and then the outcome of interest that[br]were interested in is the performance of

0:48:49.879,0:48:51.149
the text

0:48:51.149,0:48:53.879
that's the fundamental

0:48:53.879,0:48:55.359
and you will be able to

0:48:55.359,0:48:56.018
do this

0:48:56.018,0:48:59.035
over and over again as you're looking at[br]different studies and we've this is part

0:48:59.035,0:49:00.289
of the assignment

0:49:00.289,0:49:02.139
for two more

0:49:02.139,0:49:04.459
so let's practice

0:49:04.459,0:49:07.689
as we've seen the sixty location without[br]heart disease is presenting with some

0:49:07.689,0:49:09.199
nonsense shortness of breath

0:49:09.199,0:49:11.229
we're considering a p

0:49:11.229,0:49:14.489
that would be our disease or our p

0:49:14.489,0:49:19.269
protest and ask us to consider is a test[br]collabera profusion scheme

0:49:19.269,0:49:21.024
cowbell asian perfusion scan

0:49:21.024,0:49:23.939
is something that's been around for a[br]long time

0:49:23.939,0:49:25.589
it basically

0:49:25.589,0:49:28.027
in the test a patient in hale's

0:49:28.027,0:49:31.899
or radio nuclei partner

0:49:31.899,0:49:36.629
and we see where that radio nuclei[br]particle goals

0:49:36.629,0:49:40.239
and in addition the patient gets[br]injected with that same radio nuclear

0:49:40.239,0:49:41.139
particle

0:49:41.139,0:49:43.959
and we see based on the blood flow

0:49:43.959,0:49:45.249
that particle goes

0:49:45.249,0:49:46.769
we take pictures

0:49:46.769,0:49:49.849
simplistic explanation but i thought you[br]really need to know at this point

0:49:49.849,0:49:51.849
and what we're looking for is

0:49:51.849,0:49:54.029
where does the air go

0:49:54.029,0:49:56.549
that blood doesn't go

0:49:56.549,0:49:59.489
but that there's a place where the air[br]goes that the blood doesn't go that

0:49:59.489,0:50:02.669
would likely be where o'clock would be

0:50:02.669,0:50:04.399
api

0:50:04.399,0:50:07.599
but that's what happens is that the[br]clock obstructs blood flow to that

0:50:07.599,0:50:10.219
particular place

0:50:10.219,0:50:12.549
now the gold standard

0:50:12.549,0:50:16.489
four diagnosis of a pulmonary embolism[br]something we call pulmonary and

0:50:16.489,0:50:17.379
geography

0:50:17.379,0:50:20.739
which is where you were actually[br]injecting died and watching where the

0:50:20.739,0:50:22.089
blood blow goes

0:50:22.089,0:50:24.069
you see a picture of a b q scan on the[br]top there

0:50:24.069,0:50:28.939
on the bottom is a very grainy picture[br]of a pulmonary angiogram

0:50:28.939,0:50:31.409
just keep in mind that an angiogram

0:50:31.409,0:50:33.509
more costly

0:50:33.509,0:50:37.379
slightly more dangerous

0:50:37.379,0:50:38.949
the gold standard

0:50:38.949,0:50:42.539
but we wouldn't because it's costly and[br]more dangerous we wouldn't offered to

0:50:42.539,0:50:43.819
all patients

0:50:43.819,0:50:44.819
because if we did that

0:50:44.819,0:50:48.027
the risk that we would in anyone who we[br]suspect has a p

0:50:48.027,0:50:51.013
the amount of complications and cost[br]that we would entail

0:50:51.013,0:50:53.009
would be mass

0:50:53.009,0:50:56.011
that's what we're looking to see is is[br]of the few scan which is actually

0:50:56.011,0:50:58.609
fairly

0:50:58.609,0:51:00.539
really fairly

0:51:00.539,0:51:02.349
at not terribly dangerous

0:51:02.349,0:51:05.039
whether that would be good enough[br]compared to the gold standard for many

0:51:05.039,0:51:07.009
of the geography

0:51:07.009,0:51:10.229
what were interested in is diagnostic[br]performance

0:51:10.229,0:51:16.709
so that is the pico recognize the test

0:51:16.709,0:51:20.499
but before thinking about it became[br]scandal then elation perfusion scamper

0:51:20.499,0:51:23.099
first question we have to ask

0:51:23.099,0:51:26.299
kena beat you scan actually even be used

0:51:26.299,0:51:28.779
now you will be asking this question as[br]a clinician

0:51:28.779,0:51:31.039
but before you can even go to market

0:51:31.039,0:51:32.033
as a possible test

0:51:32.033,0:51:35.041
there's some fundamental questions about[br]a diagnostic test

0:51:35.041,0:51:38.599
that require some definitions that you[br]should be aware

0:51:38.599,0:51:42.299
and they thought this on to concerts[br]accuracy and precision in order for a

0:51:42.299,0:51:43.084
test to be used

0:51:43.084,0:51:47.579
in the literature and study for possible[br]use it needs to be accurate

0:51:47.579,0:51:50.399
and it needs to be precise or whining[br]about it

0:51:50.399,0:51:53.054
what accuracy means at the results of[br]the test

0:51:53.054,0:51:57.209
corresponds consistently with from[br]result

0:51:57.209,0:52:00.839
not going to result in terms of[br]diagnosing the disease

0:52:00.839,0:52:02.519
but the correct about

0:52:02.519,0:52:05.619
meaning that it'd be q skin if i object

0:52:05.619,0:52:08.709
the radio nuclei and i say it goes to[br]the long

0:52:08.709,0:52:10.959
if you go to the law

0:52:10.959,0:52:15.029
and if i inhale the radio nuclei and i[br]say he should be inhaled into the

0:52:15.029,0:52:16.569
alveolar space

0:52:16.569,0:52:21.039
it should actually be inhaled into the[br]alveolar sticks

0:52:21.039,0:52:21.729
fundamental

0:52:21.729,0:52:25.219
but keep in mind that there is a clone[br]of work that happens

0:52:25.219,0:52:28.619
prior to attest going to study

0:52:28.619,0:52:31.229
that requires this to happen

0:52:31.229,0:52:33.839
and there's a lot of science behind us

0:52:33.839,0:52:35.071
so needs to be accurate enemies

0:52:35.071,0:52:39.056
besides we're learning about the size[br]twelve decision means that if you do

0:52:39.056,0:52:43.309
with over and over again on the same[br]patient you'll get the same result

0:52:43.309,0:52:45.479
with a reliable test

0:52:45.479,0:52:50.229
the repeated values on the same sample[br]resume results in the same down

0:52:50.229,0:52:53.529
so in the same patient you do it once[br]you do it again five minutes later you

0:52:53.529,0:52:54.066
you five minutes later

0:52:54.066,0:52:56.739
missing uh... results actually happened

0:52:56.739,0:52:58.929
that's the preciseness

0:52:58.929,0:53:00.489
you need to have both

0:53:00.489,0:53:02.739
they're actually three different

0:53:02.739,0:53:04.609
possibilities that tend to happen

0:53:04.609,0:53:05.909
when early

0:53:05.909,0:53:09.109
phase studies are done and diagnostic[br]tests

0:53:09.109,0:53:10.051
the first is the one that you want

0:53:10.051,0:53:13.041
want to be highly accurate and highly[br]precise pointed out that you're good to

0:53:13.041,0:53:13.091
go

0:53:13.091,0:53:16.839
ready to go to step two and study its[br]characteristics

0:53:16.839,0:53:17.989
however

0:53:17.989,0:53:20.359
you can have something very precise

0:53:20.359,0:53:22.699
but be completely inaccurate

0:53:22.699,0:53:25.709
that's what's represented conceptually[br]by the bulls on where you have a lot of

0:53:25.709,0:53:28.017
different numbers there clustering all[br]around the same area

0:53:28.017,0:53:31.989
but it's actually not doing what you[br]think it's doing

0:53:31.989,0:53:34.149
and then there is sometimes when you[br]have

0:53:34.149,0:53:37.589
reasonable accuracy it's all clustered[br]around the bulls eye

0:53:37.589,0:53:38.929
but low precision

0:53:38.929,0:53:40.529
their hat you get different

0:53:40.529,0:53:42.839
answers each time you do it

0:53:42.839,0:53:45.039
so what do you do in these different[br]situations

0:53:45.039,0:53:48.459
well the first into a single one step to[br]your butt

0:53:48.459,0:53:51.249
the second one you gotta think about[br]calibration

0:53:51.249,0:53:56.609
and you need to reset or maybe you need[br]to relook at the reagents veteran vault

0:53:56.609,0:53:59.179
at a particular test itself

0:53:59.179,0:54:02.629
in the last one unfortunately you gotta[br]start over

0:54:02.629,0:54:06.279
if you've got a bunch of if you're a[br]test is not precise how usable could

0:54:06.279,0:54:07.559
actually be

0:54:07.559,0:54:10.029
you have to actually get the precision[br]death

0:54:10.029,0:54:12.067
again this may seem fundamental in[br]foundational

0:54:12.067,0:54:16.489
but there are so many things that don't[br]make it to market for even testing

0:54:16.489,0:54:18.449
because they don't meet these criteria

0:54:18.449,0:54:21.529
important for you to keep him

0:54:21.529,0:54:25.749
once you make it past that first phase[br]then you can decide

0:54:25.749,0:54:30.439
diagnostic performance it what the[br]diagnostic performances the o of the

0:54:30.439,0:54:32.969
pico for diagnostic tests

0:54:32.969,0:54:34.022
and so fundamentally

0:54:34.022,0:54:37.079
i would ask you to think about two[br]things

0:54:37.079,0:54:41.059
any good diagnostic study does this

0:54:41.059,0:54:43.769
they take a well-defined group of people

0:54:43.769,0:54:46.679
who are at risk for a particular[br]condition

0:54:46.679,0:54:49.099
a whole population of them and they[br]expose them to

0:54:49.099,0:54:52.159
the experimental tests

0:54:52.159,0:54:54.969
and the gold st

0:54:54.969,0:54:57.699
everyone in the study needs to have both

0:54:57.699,0:55:01.139
and if you compare the test results

0:55:01.139,0:55:02.379
experimental tests

0:55:02.379,0:55:04.679
and the gold standard

0:55:04.679,0:55:07.879
keep in mind you don't want that patient[br]population to be

0:55:07.879,0:55:11.089
everyone having the disease a hunter[br]percent of them having the disease

0:55:11.089,0:55:12.051
you need to have a fair number

0:55:12.051,0:55:15.003
of people who don't have the disease in[br]order to test

0:55:15.003,0:55:16.959
the test characteristics

0:55:16.959,0:55:20.079
well that's the fundamental premise of[br]any good diagnostic study and you'll be

0:55:20.079,0:55:22.629
able to recognize he's

0:55:22.629,0:55:26.439
what we can do is determine the strength[br]of the association

0:55:26.439,0:55:30.459
between the study results of the[br]diagnostic test

0:55:30.459,0:55:34.119
of interest and the gold standard[br]missiles he just comparing the two how

0:55:34.119,0:55:36.289
well do they compare against each other

0:55:36.289,0:55:39.679
the strength of all of that statistical[br]significance is the degree of

0:55:39.679,0:55:44.659
correlation begin the accuracy or not[br]yet received the test results all the

0:55:44.659,0:55:49.329
two different tests that are on in this[br]particular set

0:55:49.329,0:55:52.829
clinical significance is another factor[br]we're not going to talk about that

0:55:52.829,0:55:54.209
right now

0:55:54.209,0:55:58.719
well what we need to do is focus on[br]statistical significance

0:55:58.719,0:56:01.639
so before we break i'm just going to

0:56:01.639,0:56:04.689
present to you with the way that i'm[br]gonna ask you

0:56:04.689,0:56:05.799
to think about

0:56:05.799,0:56:07.091
and represent that data

0:56:07.091,0:56:11.049
from a diagnostic study that does[br]exactly what

0:56:11.049,0:56:13.979
what i'd just out

0:56:13.979,0:56:17.079
a diagnostic study you are looking at

0:56:17.079,0:56:18.349
the

0:56:18.349,0:56:21.579
performance of the test of interest

0:56:21.579,0:56:23.076
and the gold standard he's y

0:56:23.076,0:56:26.019
t

0:56:26.019,0:56:28.259
better out there to buy two table

0:56:28.259,0:56:30.119
to be able to represent

0:56:30.119,0:56:34.469
how those the study participants a sort[br]themselves based on how the test of

0:56:34.469,0:56:35.339
interested

0:56:35.339,0:56:37.909
and how the gold standard label

0:56:37.909,0:56:40.869
across the top you always

0:56:40.869,0:56:44.129
you always uh... the columns are[br]represented by those that tested

0:56:44.129,0:56:45.006
positive

0:56:45.006,0:56:48.024
for the disease based on the gold[br]standard medical center

0:56:48.024,0:56:50.023
work theoretically calling a[br]hundred-percent

0:56:50.023,0:56:54.679
therefore each identified those in the[br]population who have the disease

0:56:54.679,0:56:57.019
and those that test negative by the gold[br]standard

0:56:57.019,0:57:00.409
will be in the second call

0:57:00.409,0:57:02.419
but all of these populations

0:57:02.419,0:57:03.077
in the study

0:57:03.077,0:57:07.046
there will be some of those that also[br]tested positive based on the

0:57:07.046,0:57:11.739
experimental test you're interested

0:57:11.739,0:57:14.619
and some that test lead

0:57:14.619,0:57:16.092
and sometimes they're going to agree

0:57:16.092,0:57:18.699
with what the gold standard says

0:57:18.699,0:57:22.269
such as inbox a and boxy

0:57:22.269,0:57:24.019
sometimes they're going to disagree

0:57:24.019,0:57:25.999
with what the gold standard set

0:57:25.999,0:57:29.239
based on box b and boxy

0:57:29.239,0:57:32.024
for simplicity safe keep in mind that we[br]arent we are

0:57:32.024,0:57:36.459
assuming that the gold standard is a[br]hundred percent

0:57:36.459,0:57:39.044
so we're just gonna assume that whatever[br]the gold standard said is true

0:57:39.044,0:57:42.899
and we're comparing it against test of[br]interest

0:57:42.899,0:57:46.069
each of these boxes have different names[br]that are going to come get introduced to

0:57:46.069,0:57:47.079
you

0:57:47.079,0:57:48.589
does that work

0:57:48.589,0:57:53.729
disease are are labeled correctly by[br]experimental tasks

0:57:53.729,0:58:00.199
as having the disease based on the gold[br]standard are called true positives

0:58:00.199,0:58:01.859
their inbox it

0:58:01.859,0:58:05.339
those that are correctly labelled as not[br]having the disease by the experimental

0:58:05.339,0:58:12.699
test relative to the gold standard are[br]considered true naked

0:58:12.699,0:58:13.089
those that are

0:58:13.089,0:58:17.069
falsely labeled as having the ditsy

0:58:17.069,0:58:18.299
based on the tax

0:58:18.299,0:58:21.719
but they actually build because the gold[br]standard sent me one

0:58:21.719,0:58:26.559
are called false positives

0:58:26.559,0:58:30.689
and those that are falsely labeled at[br]not having the disease

0:58:30.689,0:58:32.349
when they actually do

0:58:32.349,0:58:34.679
are called false names

0:58:34.679,0:58:36.769
the standard nomenclature

0:58:36.769,0:58:38.009
gotta remember it

0:58:38.009,0:58:40.061
fairly straightforward false positives[br]false names

0:58:40.061,0:58:44.199
these areas of agreement these are the[br]areas of disagreement

0:58:44.199,0:58:46.049
what we're going to do no

0:58:46.049,0:58:47.009
is picked up

0:58:47.009,0:58:49.009
with our

0:58:49.009,0:58:52.069
figuring out how we use this to define[br]test characteristics

0:58:52.069,0:58:55.229
so let's take a five minute break

0:58:55.229,0:58:57.359
and then we will come back and talk[br]about

0:58:57.359,9:59:59.000
the test characteristics better rise[br]from this to my teeth