Preventive therapies: weighing the pros and cons.

The author comments on three issues raised by Dr. Kenneth G. Marshall in his series on the benefits and harms of preventive therapies, which begins in this issue on page 1493. First, because the method by which the results of clinical trials are presented markedly affects the perception of those results some measure of absolute benefit and harm must be used when the results of clinical trials are presented. Second, there is increasing interest in decision aids as a means of helping patients to understand evidence and make therapeutic choices. It is important that these aids undergo rigorous testing before they are adopted for common use. Third, evidence-based clinical practice guidelines are a welcome resource for busy clinicians. However, physicians and patients should bear in mind that interpretations of the available evidence can vary, leading to different conclusions about the appropriateness of preventive therapies.