OnlineMedEd: Epidemiology and Stats - "Diagnostic Tests"

Question 1

In a 2x2 table, ___________ is always on the top.

Answer 1

disease status

Test status is always on the side.

Question 2

Positive disease status is always on the __________ column.

Answer 2

lefthand

Question 3

Give the formula for sensitivity as well as a verbal description.

Answer 3

Sensitivity = TP / (TP + FN)

Sensitivity shows how many people with the disease will test positive. How many people with the disease will test positive? Sensitive tests have low false negative rate.

Question 4

Give the formula for specificity as well as a verbal descriptor.

Answer 4

Specificity = TN / (TN + FP)

Specificity shows how many people without the disease will test negative. How many people with the disease will test negative? Specific tests have low false positive rate.

Question 5

Give the formula for PPV as well as a verbal description.

Answer 5

PPV = TP / (TP + FP)

PPV is the likelihood that a positive result is true. It increases with increased prevalence.

Question 6

Give the formula for NPV as well as a verbal description.

Answer 6

NPV = TN / (TN + FN)

NPV is the likelihood that a negative result is true. It decreases with increased prevalence.