Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

foundations of clinical medicine > Evidence: > Flashcards

Evidence: Flashcards

1
Q

What is diagnostic intuition?

A
  • having a feeling that someone has an illness.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

is a pothole evidence?

A
  • it is evidence because the road was altered but the question is evidence of what?
  • there is no evidence unless we have a hypothesis or evidence from something.
  • could be evidence that people arent paying their taxes, climate change, corrupt government,
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is missing in the Canadian amulet example?

A
  • the number of people who haven’t been attacked either without the amulet.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are liklihood ratios?

A
  • a number representing the diagnostic usefulness of a test.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

how do we calculate likelihood ratios?

A
  • the probability that you’d see some evidence if your hypothesis were true/ probability that you’d see the exact same evidence if your hypothesis were false.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how are likelihood ratios represented?

A
  • they range from 0 to infinity (can never be a negative number).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what does a LR of 1 mean?

A

it is useless.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what does an LR of greater than 1 mean?

A
  • it increases the probability ( the higher the better).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what does an LR less than 1 mean?

A
  • it decreases the probability (the lower the better).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what does LR+ mean?

A
  • it means the finding was present, not that it necessarily increases the probability.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what does an LR- mean?

A
  • means that the finding was absent, not that it is a negative number and not necessarily that it decreases the probability
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why is it beneficial for clinicians to understand?

A
  • The clinician who understands the evidence can then approach his or her own patients with the confidence and wisdom that would have developed had they personally examined and learned from the thousands of patients reviewed in the studies of this book.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What test if positive would most increase the probability of hyperthyroidism?
Pulse: 90 bpm LR+= 4.4 LR- 0.2
Skin moist and warm LR+= 6.7 LR- 0.7
Enlarged thyroid LR+= 2.3 LR- 0.1
Eyelid retraction LR+= 31.5 LR-= 0.7
Eyelid lag LR+= 17.5 LR-= 0.8
Fine finger tremor LR+=11.4 LR-= 0.3

Wayne Index
<11 0.04
11-19 points= NS
20 points 18.2

A

eyelid retraction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What test if negative would most increase the probability of hyperthyroidism?
Pulse: 90 bpm LR+= 4.4 LR- 0.2
Skin moist and warm LR+= 6.7 LR- 0.7
Enlarged thyroid LR+= 2.3 LR- 0.1
Eyelid retraction LR+= 31.5 LR-= 0.7
Eyelid lag LR+= 17.5 LR-= 0.8
Fine finger tremor LR+=11.4 LR-= 0.3

Wayne Index
<11 0.04
11-19 points= NS
20 points 18.2

A

enlarged thyroid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What test would most decrease the probability of hyperthyroidism?
Pulse: 90 bpm LR+= 4.4 LR- 0.2
Skin moist and warm LR+= 6.7 LR- 0.7
Enlarged thyroid LR+= 2.3 LR- 0.1
Eyelid retraction LR+= 31.5 LR-= 0.7
Eyelid lag LR+= 17.5 LR-= 0.8
Fine finger tremor LR+=11.4 LR-= 0.3

Wayne Index
<11 0.04
11-19 points= NS
20 points 18.2

A

less than 11 points on the Wayne index.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What could go wrong when using multiple likelihood ratios?

A
  • overestimations.
  • main concern, is double counting evidence.
  • can not apply both charts with the same condition.
  • this will give you an extreme estimate.
  • For example eyelid retraction and eyelid lag, Dwayne index may also include some of these.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why is it important to be aware of double counting?

A
  • some findings are closely correlated or even included in other findings.
  • e.g. increased patellar reflex and increased ankle jerk reflex.
  • e.g. 4/5 findings on ABCDE score for melanoma and irregular borders for leison.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what do we have to avoid when looking at likelihood ratios?

A
  • avoid using more than one of the correlated findings.
  • knowledge of physiology will help with this, otherwise, your probability estimate will be too extreme.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

When choosing between options you should?

A
  • pick the one that provides the best evidence.
20
Q

What tests should not be included in calculations because they would represent double-counting evidence?
What test if positive would most increase the probability of hyperthyroidism?
Pulse: 90 bpm LR+= 4.4 LR- 0.2
Skin moist and warm LR+= 6.7 LR- 0.7
Enlarged thyroid LR+= 2.3 LR- 0.1
Eyelid retraction LR+= 31.5 LR-= 0.7
Eyelid lag LR+= 17.5 LR-= 0.8
Fine finger tremor LR+=11.4 LR-= 0.3

Wayne Index
<11 0.04
11-19 points= NS
20 points 18.2

A
  • eyelid lag and eyelid retraction.
21
Q

why is it important to be aware of what you are asking?

A
  • questions pertaining to a condition could also apply to individuals without the condition.
  • example; scoring 4 points both with/without alcohol abuse.
22
Q

What can we do if we cant find likelihood ratios in the literature?

A
  • we can calculate them using sensitivity and specificity.
23
Q

what is sensitivity?

A
  • in patients who have the disease, the probability that the test will be positive.
  • the probability of seeing evidence if your hypothesis were true.
  • Sensitivity: the ability of a test to correctly identify patients with a disease.
24
Q

what is specificity?

A
  • in patients who don’t have the disease the probability that your test will be negative.
  • the complement of the probability that you would see the same evidence if your hypothesis were false.
  • Specificity: the ability of a test to correctly identify people without the disease.
25
Q

What is the formula for calculating positive likelihood ratios?

A

LR+= sensitivity/ (1- specificity.)

26
Q

What is the formula for calculating negative likelihood ratios?

A

LR+= (1-sensitivity)/ specificity.

27
Q

How do we estimate liklihood ratios?

A
  • you compare a group of people with a condition to those without a condition with respect to the finding you are looking for (symptoms)
  • the ratio of these two is your estimated likelihood ratio.
28
Q

How is applying evidence intuitive?

A

in that the more certain you are initially the harder it should be to change your mind.

29
Q

how is applying evidence unintuitive?

A
  • the more uncertain you are initially the less evidence you need to change your mind.
  • it takes more evidence to go from 1-5% than from 51 to 55% certainty (though both increase probability by 4%).
30
Q

For moderate pretest possibilities, how do we estimate changes in probability?

A
  • We can use Mcgee’s chart.
  • 10 = +45
  • 5 = +30
  • 2 = +15
  • 1 = 0
  • 0.5 = -15
  • 0.2 = -30
  • 0.1 = -45
31
Q

How can we estimate probabilities for low pre-test probabilities?

A
  • you can multiply the LR by the pretest probability.
  • example; LR=5 and pretest probability 2%.
  • 2x 5= 10%
32
Q

what are clinical decision rules?

A
  • there may be tables associated with specific conditions with post-test probabilities already calculated.
  • example pneumonia.
33
Q

What is a positive predictive value (PPV)?

A
  • the probability of disease given that a test was positive.
34
Q

What is a negative predictive value?

A
  • the probability of disease given that the test was negative.
35
Q

What does assumption mean?

A
  • your patient’s pretest probability is the same as those in the study that determined the PPV/NPV.
  • it is as if it has already done the LR calculation for you but assumed pretest probability.
  • i.e. simpler but not as accurate (depending on pretest probability) as applying LR’s
36
Q

What are pathognomic findings?

A
  • pathos= disease and gnomom= indicator.
  • findings that, if present, strongly increases the probability of a condition.
  • i.e. High LR+; not necessarily particularly sensitive but highly specific.
37
Q

What are Sine Qua Non-findings?

A
  • without which it could not be.
  • findings which if absent strongly decrease the probability of a condition.
  • i.e. low LR- (close to 0).
38
Q

What is the process of finding evidence in practise?
5 steps.

A
  1. recognize the need for more evidence.
  2. choose a test (question, physical exam, lab test).
  3. perform the test correctly. for labs, this may be the responsibility of the technician.
  4. interpret the results correctly.
  5. repeat steps 1-4 until you cross the threshold.
39
Q

What are the 4 common errors in practice when collecting evidence?

A
  1. fail to recognize the need for more evidence (premature closure).
  2. poorly chosen or missed test (question, physical exam or lab etc.)
  3. incorrectly performed test (esp. physical exam).
  4. incorrect interpretation (lack of knowledge and bias).
40
Q

what is premature closure?

A
  • fil to recognize the need for more evidence.
41
Q

What is informative value?

A

the value of a test or information of information collected. you can have a lot of information but that does not mean it will be useful in helping your persons case in diagnosis.

42
Q

What is the difference between experts and novice clinicians when it comes to evidence collection?

A
  • Novices generally collect more DATA while having lower diagnostic accuracy.
  • experts generally have less info collected but higher diagnostic accuracy because the data they collect has a higher informative value.
43
Q

What can evidence usefully be described by?

A

likelihood ratios.

44
Q

what are likelihood ratios?

A
  • are a ratio of the probabilities of a finding being present if the hypothesis were true versus if it were false.
45
Q

What do the different LR values indicate?

A
  • LR of 0 indicates no evidence.
  • LRs >1 indicates an increase in the probability of the hypothesis.
  • LRs < 1 indicate a decrease in the probability of your hypothesis.

foundations of clinical medicine (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions