A test has sensitivity 90% and specificity 85%. The Likelihood Ratio of a Positive test (LR+) is:
- A 6.0 ✓
- B 3.0
- C 9.0
- D 10.5
Correct answer: A. 6.0
Explanation
LR+ = Sensitivity / (1 – Specificity) = 0.90 / 0.15 = 6.0. LR+ >10 provides strong diagnostic evidence; 5–10 moderate; 2–5 small; <2 minimal. An LR+ of 6 means a positive test result is 6 times more likely to occur in a truly diseased person than in a healthy one. LR+ is used with Bayes' theorem to update pre-test probability to post-test probability using nomograms or Fagan's plot.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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