Question

Describe the following for a given test: 
Positive predictive value. 
 

Hint:

Positive predictive value is influenced by the prevalence of the disease in the population. Higher disease prevalence increases PPV.

Answer 1

Step 1: Defining Positive Predictive Value (PPV).
Positive Predictive Value refers to the probability that subjects with a positive test result actually have the disease. It indicates the likelihood that a positive test result is a true positive.

Step 2: Formula for Positive Predictive Value.
\[ \text{PPV} = \frac{\text{True Positives}}{\text{True Positives + False Positives}} \] Where:
- True Positives (TP): The number of people who have the disease and test positive.
- False Positives (FP): The number of people who do not have the disease but test positive.

Step 3: Conclusion.
A high PPV means that a positive test result is highly likely to represent a true positive, and the disease is present. This is important for ensuring that individuals who test positive truly have the disease.