American Board of Surgery Qualifying Exam (ABS QE) Practice Test

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Prepare for the American Board of Surgery Qualifying Exam with detailed quizzes. Study with flashcards and multiple-choice questions to master the ABS QE topics. Get all the hints and explanations you need to succeed on your first attempt!

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Which formula represents specificity in diagnostic testing?

TP / (TP + FN)
TN / (TN + FP)
TP / (TP + FP)
FN / (FN + TN)

The correct answer is: TN / (TN + FP)

Specificity is a measure of a diagnostic test's ability to correctly identify those individuals who do not have the disease. It represents the proportion of true negative results in all individuals who are actually free of the condition. The correct formula for specificity is derived from the definition involving true negatives (TN) and false positives (FP). It is calculated as the number of true negatives divided by the total number of actual negatives, which comprises true negatives plus false positives. This ratio indicates how well the test can identify healthy individuals, making its interpretation crucial in evaluating the effectiveness of a diagnostic test. In contrast, the other formulas pertain to different measures of a diagnostic test's performance. The first option, for instance, represents sensitivity, which focuses on true positives (TP) and false negatives (FN). The remaining options either mix the parameters related to sensitivity or address distinct aspects of test accuracy that are not related to specificity.