In the context of screening, the Likelihood Ratio Positive (LR+) combines sensitivity and specificity into a single measure. For a test with sensitivity 85% and specificity 90%, LR+ is:

• A 6.5
• B 8.5 ✓
• C 9.4
• D 7.0

Explanation

LR+ = Sensitivity / (1 − Specificity) = 0.85 / (1 − 0.90) = 0.85 / 0.10 = 8.5. An LR+ of 8.5 means a positive test result is 8.5 times more likely in a person with disease than without. LR+ > 10 is considered excellent; 5-10 good; 2-5 moderate; <2 poor. LR+ is particularly useful because it is independent of disease prevalence and can be combined with pre-test probability using Bayes' theorem.

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

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Written and medically reviewed by the StethoPrep medical team.