Negative predictive value is defined as

Negative predictive value is defined as

• A. NPV = TP / (TP + FN)
• B. NPV = TN / (TN + FN)
• C. NPV = TP / (TP + FP)
• D. NPV = TN / (TN + FP)

Answer: (B)

Negative predictive value reflects the probability that a person truly does not have the disease when the test result is negative. It is calculated as the number of true negatives divided by all negatives (true negatives plus false negatives): TN / (TN + FN). This means among everyone who tested negative, how many are actually disease-free. This is different from sensitivity (which looks at how well the test identifies those with disease) and specificity (how well the test identifies those without disease), as well as from the positive predictive value (which answers, among those who test positive, how many truly have the disease). The NPV specifically answers the question: if the test result is negative, what proportion are truly disease-free? Context: NPV depends on disease prevalence. When disease is rare, most people are disease-free, so a negative result is likely a true negative and NPV is high. As disease becomes more common, there are more false negatives among those testing negative, and the NPV decreases.

Negative predictive value reflects the probability that a person truly does not have the disease when the test result is negative. It is calculated as the number of true negatives divided by all negatives (true negatives plus false negatives): TN / (TN + FN). This means among everyone who tested negative, how many are actually disease-free.

This is different from sensitivity (which looks at how well the test identifies those with disease) and specificity (how well the test identifies those without disease), as well as from the positive predictive value (which answers, among those who test positive, how many truly have the disease). The NPV specifically answers the question: if the test result is negative, what proportion are truly disease-free?

Context: NPV depends on disease prevalence. When disease is rare, most people are disease-free, so a negative result is likely a true negative and NPV is high. As disease becomes more common, there are more false negatives among those testing negative, and the NPV decreases.