What is the correct formula for calculating positive predictive value (PPV)?

Positive predictive value (PPV) measures the probability that individuals with a positive test result truly have the disease. The formula for calculating PPV is defined as the number of true positives (TP) divided by the total number of positive test results, which includes both true positives and false positives (FP).

Thus, the formula can be represented as TP/(TP + FP). By using this formula, healthcare practitioners can assess the effectiveness of a diagnostic test in identifying the presence of a condition among those who test positive. A high PPV suggests that a positive test result is a reliable indicator of disease, while a low PPV indicates that many individuals who test positive may not actually have the condition.

The other options presented do not accurately reflect the concept of positive predictive value. For instance, one option focuses on the ratio of true positives to false negatives, which relates to sensitivity rather than predictive value. Another option considers true negatives in the context of calculating predictive values, which is not relevant for PPV. Understanding these distinctions is important for interpreting test results and making informed clinical decisions.