SBA — Single Best Answer · Review
Question 688
Statistics → Epidemiology
Classification
Question
SSBAQuestion Header
Statistics
Question Stem
In a group of 200 individuals known to have a disease, 170 have a positive diagnostic test and 30 have a negative test. What is the sensitivity of the test?
Options
A
15%
B
70%
C
85%
D
88%
E
92%
Explanation
Sensitivity is calculated as true positives divided by true positives plus false negatives. Here, 170 individuals with disease test positive and 30 with disease test negative. Therefore sensitivity = 170/(170 + 30) = 170/200 = 0.85, or 85%. Sensitivity measures the ability of the test to identify correctly those who have the disease.
Option Validity
A) 15% represents the false-negative proportion in this group.
B) This does not follow from the sensitivity formula.
D) The denominator must include all 200 individuals with disease.
E) The supplied figures yield 85%, not 92%.
Further Reading
Saxena - MRCOG-1 Basic Sciences, Chapter 10: Epidemiology/Statistics, Printed p.287.