Defensive Diagnostic Testing: A Case of Stolen Utility?

For most physicians, the experience of missing a treatable diagnosis or of making a treatment decision that leads to a bad outcome is disturbing, to say the least. In addition, many physicians believe that their liability for diagnostic or treatment errors has increased. A natural response to these concerns is to rely more heavily on diagnostic tests. We have all heard the objection that the use of tests to reduce malpractice liability-defensive testing-generates unwarranted medical expenditures.

In this issue of Medical Decision Making, DeKay and Asch show that there is another problem to consider: Defensive testing harms patients. As defined by DeKay and Asch, defensive testing occurs when a clinician uses a test in circumstances in which it would not be warranted based solely on a patient's medical condition and preferences; rather, the clinician uses the test because of concern about his or her liability for treatment errors. Their analysis indicate8 that defensive testing reduce8 the expected utilities of all patients for whom test ordering is changed because of liability considerations. This result will surprise some clinicians-certain authors have even argued that defensive testing may help patients. Why does defensive testing harm patients? How much of a problem is it?