You are conducting a screening for osteoporosis at an assisted living facility. You recruit 171 subjects and 34 screen positive for osteoporosis. You have 17 people who have osteoporosis confirmed by dexascan but only 14 of them screened positive. Three people who have osteoporosis screened negative. What is the efficacy of your screen?

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Quizplus · Accepted Answer

The efficacy of a screening test is often measured by its sensitivity and specificity. Sensitivity is the ability of the test to correctly identify those with the disease. Here, sensitivity = (True Positives) / (True Positives + False Negatives) = 14 / (14 + 3) = 14 / 17 = 82.35%. However, the question asks for efficacy, which can be interpreted as the proportion of true results (both true positives and true negatives) in the population. True negatives = 171 - 34 - 3 = 134. Efficacy = (True Positives + True Negatives) / Total Population = (14 + 134) / 171 = 148 / 171 = 86.5%.

You Are Conducting a Screening for Osteoporosis at an Assisted