A screening test for a rare disease has a high sensitivity and specificity. If this test is applied to a population where the disease prevalence is very low, which of the following is most likely to be true?

Explanation

Positive Predictive Value (PPV) is the probability that an individual with a positive test result truly has the disease. When disease prevalence is very low, even a highly specific test will generate a relatively large number of false positives compared to true positives. This is because the number of true positives is inherently small due to low prevalence, while the number of false positives (1-specificity) applied to a large healthy population can still be substantial. Consequently, the PPV will be low. Conversely, the Negative Predictive Value (NPV) tends to be high in low prevalence settings. Sensitivity and specificity are intrinsic characteristics of the test and do not change with disease prevalence.