Which term refers to the ratio of true positives to the total number of actual positives in a test?

The term that refers to the ratio of true positives to the total number of actual positives in a test is sensitivity. Sensitivity measures a test's ability to correctly identify those with the condition (true positives) out of all individuals who actually have the condition (true positives plus false negatives). This means that a high sensitivity indicates that the test is effective in detecting the disease when it is present, which is crucial in clinical settings for ensuring that patients who have the condition are accurately diagnosed.

In contrast, other terms such as specificity, accuracy, and positive predictive value have different definitions. Specificity pertains to the test’s ability to identify those without the condition (true negatives) among all those who do not have the disease (true negatives plus false positives). Accuracy refers to the overall ability of the test to correctly classify both positive and negative cases. Positive predictive value measures the proportion of true positives among all positive test results, which is influenced by both the test's sensitivity and the prevalence of the condition in the population being tested.