A positive likelihood ratio (LR+) of 12 for a rapid antigen test means:
- A A positive result is 12 times more likely in a truly diseased person than in a truly non-diseased person ✓
- B The test has a sensitivity of 12% in the population studied
- C For every 12 true positives, there is 1 false positive
- D The PPV of the test is 12 times higher than its NPV
Correct answer: A. A positive result is 12 times more likely in a truly diseased person than in a truly non-diseased person
Explanation
LR+ = Sensitivity / (1 − Specificity) = probability of a positive test in disease / probability of a positive test without disease. An LR+ of 12 means a positive result is 12 times more likely in a person with the disease than without, substantially raising post-test probability. LR+ > 10 is considered strong evidence to rule in disease; LR+ < 0.1 is strong evidence to rule out (with LR−).
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.