Sensitivity vs. Specificity: The Ultimate USMLE Guide with Mnemonics

Sensitivity = TP / (TP + FN). Of all people who HAVE the disease, what percentage tested positive? Specificity = TN / (TN + FP). Of all people who DON'T have the disease, what percentage tested negative?

Key Mnemonics

• SnNOut: Sensitivity, Negative result, Rules OUT disease
• SpPIn: Specificity, Positive result, Rules IN disease

PPV and NPV

PPV = TP / (TP + FP). NPV = TN / (TN + FN). Both are affected by disease prevalence.

Try our 2x2 Table Calculator | Practice Questions