LR+ is computed as which formula?

LR+ is computed as which formula?

• A. (1 - sensitivity) / specificity
• B. (1 - sensitivity) / specificity
• C. sensitivity / (1 - specificity)
• D. (specificity - sensitivity) / (1 - specificity)

Answer: (C)

Likelihood ratios quantify how a test result changes the odds of disease. The positive likelihood ratio compares the probability of a positive result in someone with disease to the probability of a positive result in someone without disease. It is computed as LR+ = sensitivity / (1 - specificity). here, sensitivity is the true-positive rate (probability the test is positive when disease is present), and (1 - specificity) is the false-positive rate (probability the test is positive when disease is absent). This ratio shows how much a positive result shifts the odds toward having the disease—the larger the LR+, the stronger the evidence. For example, with sensitivity 0.8 and specificity 0.9, LR+ = 0.8 / 0.1 = 8, meaning a positive result increases the odds of disease by eightfold. The other formulas don’t reflect this relationship between true positives and false positives, so they aren’t used.

Likelihood ratios quantify how a test result changes the odds of disease. The positive likelihood ratio compares the probability of a positive result in someone with disease to the probability of a positive result in someone without disease. It is computed as LR+ = sensitivity / (1 - specificity). here, sensitivity is the true-positive rate (probability the test is positive when disease is present), and (1 - specificity) is the false-positive rate (probability the test is positive when disease is absent). This ratio shows how much a positive result shifts the odds toward having the disease—the larger the LR+, the stronger the evidence. For example, with sensitivity 0.8 and specificity 0.9, LR+ = 0.8 / 0.1 = 8, meaning a positive result increases the odds of disease by eightfold. The other formulas don’t reflect this relationship between true positives and false positives, so they aren’t used.