How is the positive predictive value accurately calculated from the carotid duplex studies?

To calculate the positive predictive value (PPV) in the context of carotid duplex studies, the correct formula involves dividing the number of true positive results by the total number of positive results (the sum of true positives and false positives).

In this case, the numerator (true positives) is represented by 53, which signifies the number of correct diagnoses made by the duplex studies. The denominator (total positive results) combines this number with the false positives. In this scenario, the total number of positive results is 61, which includes the true positives as well as false positives.

Thus, the PPV is calculated as 53 divided by 61, giving the probability that patients with a positive test truly have the condition being assessed. This calculation reflects the effectiveness of the carotid duplex studies in accurately identifying patients with carotid artery disease, which is crucial for making informed clinical decisions.