Screening Test Specifics

Question 1

What is TP = true positive; FP = false positive; TN = true negative; FN = false negative?

Answer 1

TP = test positive & disease present
FP = test positive & disease absent

TN = test negative & disease absent
FN = test negative & disease present

Question 2

What is ‘sensitivity’?

Answer 2

The proportion of patients with the condition who have a +ve test result.

Question 3

What is ‘specificity’?

Answer 3

Proportion of patients without the condition who have a negative test result

Question 4

Formula for sensitivity?

Answer 4

TP / (TP + FN)

Question 5

Formula for specificity?

Answer 5

TN / (TN + FP)

Question 6

Define positive predictive value

Answer 6

The chance that the patient has the condition if the diagnostic test is positive.

Question 7

Define negative predictive value

Answer 7

The chance that the patient does not have the condition if the diagnostic test is negative

Question 8

Formula for positive predictive value?

Answer 8

TP / (TP + FP)

Question 9

Formula for negative predictive value?

Answer 9

TN / (TN + FN)