The dangers of false-positive and false-negative test results: false-positive results as a function of pretest probability.

This article focuses on the following key points of improving clinicians' use of laboratory tests: (1) laboratory tests are always imperfect, but some are much more imperfect than others; (2) limitations in human cognition compound the potential for misinterpretation of test results; (3) false-positive and false-negative laboratory results can lead to serious patient harm; and (4) judicious use of laboratory tests can help mitigate potential harm from spurious results.