In a study, a diagnostic test for pulmonary tuberculosis is evaluated. Among 200 truly positive patients, 170 test positive. Among 300 truly negative individuals, 240 test negative. What is the positive likelihood ratio (LR+) of this test?

• A 2.83
• B 3.60
• C 5.67
• D 4.25 ✓

Explanation

Sensitivity = 170/200 = 0.85; Specificity = 240/300 = 0.80. LR+ = Sensitivity / (1 - Specificity) = 0.85 / 0.20 = 4.25. LR+ above 10 is considered strong evidence for disease; 4.25 indicates moderate value. Options A, B, and D do not correspond to the correctly computed values using these figures.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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