[Roaming through methodology. XXXII. False test results]

Abstract

The number of requests for diagnostic tests is rising. This leads to a higher chance of false test results. The false-negative proportion of a test is the proportion of negative test results among the diseased subjects. The false-positive proportion is the proportion of positive test results among the healthy subjects. The calculation of the false-positive proportion is often incorrect. For example, instead of 1 minus the specificity it is calculated as 1 minus the positive predictive value. This can lead to incorrect decision-making with respect to the application of the test. Physicians must apply diagnostic tests in such a way that the risk of false test results is minimal. The patient should be aware that a perfectly conclusive diagnostic test is rare in medical practice, and should more often be informed of the implications of false-positive and false-negative test results.