**PPV (Positive Predictive Value) Explanation**

**Core Concept**
Positive Predictive Value (PPV) is a measure of the probability that a positive test result is truly positive. It is calculated as the number of true positive results divided by the sum of true positive and false positive results. PPV is an important concept in clinical decision-making, as it helps clinicians determine the likelihood of a disease given a positive test result.

**Why the Correct Answer is Right**
The correct answer is related to the formula for calculating PPV. PPV is calculated as TP / (TP + FP), where TP is the number of true positive results and FP is the number of false positive results. This formula can be rearranged to show that PPV is inversely proportional to the prevalence of the disease. In other words, as the prevalence of the disease increases, the PPV decreases, assuming a fixed number of true and false positive results.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the relationship between PPV and disease prevalence. While PPV is related to disease prevalence, it is not directly proportional to it.

**Option B:** This option is incorrect because it does not accurately describe the formula for calculating PPV. PPV is calculated as TP / (TP + FP), not as TP / (TN + FP).

**Option C:** This option is incorrect because it does not accurately describe the relationship between PPV and disease prevalence. While PPV can be affected by disease prevalence, it is not directly proportional to it.

**Clinical Pearl / High-Yield Fact**
A high PPV indicates that a positive test result is likely to be true, but a low PPV suggests that a positive test result may be false. Clinicians should always consider the PPV of a test, as well as the pre-test probability of disease, when interpreting test results.

**Correct Answer: D. PPV is inversely proportional to the prevalence of the disease.**