🏥 USMLE Exam Prep

Likelihood ratios combine sensitivity and specificity to indicate:

A Treatment effectiveness
B How much a test result changes the probability of disease — positive LR increases and negative LR decreases probability
C Prevalence
D Cost-effectiveness

✓ Correct Answer: Option B

LR+: sensitivity/(1-specificity) — how much positive result increases disease probability. LR-: (1-sensitivity)/specificity — how much negative result decreases probability. Use with Fagan nomogram.

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