Given sensitivity 90% and specificity 80%, which pair represents LR+ and LR- respectively?

Given sensitivity 90% and specificity 80%, which pair represents LR+ and LR- respectively?

• A. LR+ = 2.25; LR- = 0.4
• B. LR+ = 4.5; LR- = 0.125
• C. LR+ = 9; LR- = 0.8
• D. LR+ = 3.6; LR- = 0.2

Answer: (B)

In likelihood ratios, LR+ shows how much the odds of disease increase with a positive test, and LR- shows how much the odds decrease with a negative test. They come from the formulas LR+ = sensitivity / (1 − specificity) and LR− = (1 − sensitivity) / specificity. With sensitivity 0.90 and specificity 0.80, LR+ = 0.90 / (1 − 0.80) = 0.90 / 0.20 = 4.5, and LR− = (1 − 0.90) / 0.80 = 0.10 / 0.80 = 0.125. Therefore, the pair is LR+ = 4.5 and LR− = 0.125.

In likelihood ratios, LR+ shows how much the odds of disease increase with a positive test, and LR- shows how much the odds decrease with a negative test. They come from the formulas LR+ = sensitivity / (1 − specificity) and LR− = (1 − sensitivity) / specificity. With sensitivity 0.90 and specificity 0.80, LR+ = 0.90 / (1 − 0.80) = 0.90 / 0.20 = 4.5, and LR− = (1 − 0.90) / 0.80 = 0.10 / 0.80 = 0.125. Therefore, the pair is LR+ = 4.5 and LR− = 0.125.