[2] Diagnostic Research Design

Question 1

Do you need a diagnosis if pretest probability is 100%?

Answer 1

No, it is not needed

Question 2

Define: Treatment Threshold

Answer 2

Probability above which diagnosis is sufficiently likely to warrant treatment

Question 3

What is the effect of a greater adverse effect of treatment on the Treatment Threshold?

Answer 3

Higher Threshold

Question 4

What is the effect if the next test the patient has to be subjected to is more invasive than the current test to be performed on the Treatment Threshold?

Answer 4

Lowered Threshold

Prevents more people from being subjected to the next more invasive test

Question 5

Define: Test/Diagnostic Threshhold

Answer 5

Probability below which a diagnosis warrants no further consideration

Question 6

What is the effect of a serious missed diagnosis on the Test/Diagnostic Threshold?

Answer 6

Lowered Threshold

Missing diagnosis would be fatal, lowering it would ensure more people to take further tests to confirm

Question 7

What is the effect if the next test to be done is riskier than the current test on the Test/Diagnostic Threshold?

Answer 7

Higher Threshold

This is done to ensure less people take the riskier next test if they don’t reach the high enough diagnosis warrant in the first place

Question 8

[Formula]

Likelihood Ratio

Answer 8

Probability of Person w/ the Disease Testing Positive / Probability of a Person w/o the Disease Testing Negative

Question 9

[Interpretation]

LR > 1

Answer 9

Increased disease probability

Question 10

[Interpretation]

LR < 1

Answer 10

Decreased disease probability

Question 11

[T/F]

Diagnostic tests with LRs close to 1 have practical significance

Answer 11

F

Goal is create a significant increase in the post test probability as compared to pre test probability

Question 12

[Interpretation]

LRs > 10 and < 0.1

Answer 12

Large and often conclusive

Question 13

[Interpretation]

LRs 5-10 and 0.1-0.2

Answer 13

Moderate Shifts

Question 14

[Interpretation]

LRs 1-2 and 0.5-1

Answer 14

Small and Rarely Important

Question 15

[Interpretation]

LRs 5-10 and 0.2-0.5

Answer 15

Small but Sometimes Important

Question 16

Definition: Gold Standard

Answer 16

Accepted definition of disease and can dictate presence or absence of it

Question 17

[Gold Standard]

Pulmonary TB

Answer 17

Chest X-Ray
Histopathology
Autopsy
Anti-Kochs
Sputum Culture

Question 18

[Gold Standard]

Pneumonia

Answer 18

Chest X-Ray
Histopathology
Sputum Culture

Question 19

[Gold Standard]

Systemic Lupus Erythematosus

Answer 19

Expert’s Opinion

Question 20

[Gold Standard]

Embolic CVD

Answer 20

CT Scan + 2D Echo

Need Both

Question 21

Definition: Sensitivity

Answer 21

Probability of a positive test among diseased

Question 22

Sensitive tests are more important for generalists or specialists?

Why?

Answer 22

Generalists

To not miss people with the disease

Question 23

Definition: Specificity

Answer 23

Probability of a test being negative among non-diseased people

Question 24

A positive test is more helpful for Specific or Sensitive tests?

Answer 24

Specific Tests

Question 25

Specific tests are more important for generalists or specialists?

Why?

Answer 25

Specialists

To help confirm diagnosis

Question 26

Definition: Accuracy

Answer 26

Proportion of people correctly diagnosed by tests as either having the disease or not having it

Question 27

Differentiate:

(+) Predictive Value
(-) Predictive Value

Answer 27

( + ): Probability that patient has the disease given a + test result

( - ): Probability that patient does not have the disease given a - test result

Question 28

Define: Kappa Statistics

Answer 28

Measures agreement beyond chance

Question 29

[Interpretation]

K = 1 or 100%

Answer 29

Perfect Agreement

Question 30

[Interpretation]

K > 0.80

Answer 30

Excellent Agreement

Question 31

[Interpretation]

0.60 < K <= 0.80

Answer 31

Good Agreement

Question 32

[Interpretation]

0.40 < K <= 0.60

Answer 32

Fair Agreement

Question 33

[Interpretation]

0 < K <= 0.40

Answer 33

Poor Agreement

Question 34

[Interpretation]

K = 0

Answer 34

Chance Agreement