L11 - EXAMINATION DIAGNOSIS ACCURACY

Question 1

What is a cross-sectional study in the context of diagnostic accuracy?

Answer 1

Blind and independent comparison of the test under study versus the diagnostic reference standard in a population of consecutive patients.

Question 2

What is the index test?

Answer 2

Diagnostic test or procedure under investigation.

Question 3

What is the reference test?

Answer 3

Referred to as gold standard, the best available method or procedure used to confirm presence or absence of disease.

Question 4

What does a true positive (TP) indicate in a 2x2 table?

Answer 4

Both index & reference test identify condition.

Question 5

What does a false positive (FP) indicate in a 2x2 table?

Answer 5

Index test identifies condition, but reference test does not.

Question 6

What does a false negative (FN) indicate in a 2x2 table?

Answer 6

Index test fails to identify condition that reference test confirms.

Question 7

What does a true negative (TN) indicate in a 2x2 table?

Answer 7

Both tests confirm absence of condition.

Question 8

How is sensitivity defined?

Answer 8

Probability of positive test in patients with disease.

Question 9

What is the formula for sensitivity?

Answer 9

SN = TP / (TP + FN)

Question 10

How is specificity defined?

Answer 10

Probability of negative test in patients without disease.

Question 11

What is the formula for specificity?

Answer 11

SP = TN / (TN + FP)

Question 12

What does a higher value indicate in sensitivity and specificity?

Answer 12

Higher = better.

Question 13

What do sensitivity and specificity fail to provide?

Answer 13

Exact probability of presence.

Question 14

What does the acronym SNnOUT stand for?

Answer 14

If test has high sensitivity & is negative, pathology can be ruled out.

Question 15

What does the acronym SPpIN stand for?

Answer 15

If test has high specificity & is positive, pathology can be ruled in.

Question 16

Which tests are typically conducted before those with high specificity?

Answer 16

Tests that have high sensitivity.

Question 17

What is the positive predictive value (PPV)?

Answer 17

Probability that person with positive test has disease.

Question 18

What is the formula for positive predictive value (PPV)?

Answer 18

PPV = TP / (TP + FP)

Question 19

What is the negative predictive value (NPV)?

Answer 19

Probability that person with negative test has disease.

Question 20

What is the formula for negative predictive value (NPV)?

Answer 20

NPV = TN / (TN + FN)

Question 21

What do predictive values depend on?

Answer 21

Prevalence of pathology.

Question 22

What is the purpose of likelihood ratios?

Answer 22

Determine probability of having a condition after a positive or negative test result.

Question 23

What does a high positive likelihood ratio (LR+) indicate?

Answer 23

Better test performance.

Question 24

What is the formula for positive likelihood ratio (LR+)?

Answer 24

LR+ = SN / (1 – SP)

Question 25

What does a low negative likelihood ratio (LR-) indicate?

Answer 25

Better test performance.

Question 26

What is the formula for negative likelihood ratio (LR-)?

Answer 26

LR- = (1 – SN) / SP

Question 27

What are the best diagnostic test accuracy values?

Answer 27

Likelihood ratios.

Question 28

What do ROC curves help identify?

Answer 28

Best cut-off for test performance.

Question 29

What does the area under the curve (AUC) represent?

Answer 29

Overall measure of test accuracy.

Question 30

What is QUADAS-2?

Answer 30

Gold standard for assessing risk of bias of studies.

Question 31

What are the components assessed by QUADAS-2?

Answer 31

• Patient selection
• Index test
• Reference standard
• Flow & timing

Question 32

True or False: Standard meta-analysis is suitable for diagnostic accuracy.

Answer 32

False.

Question 33

What does bivariate meta-analysis provide?

Answer 33

Pooled estimates for sensitivity & specificity.