Evidence-based medicine: not a slam dunk.

Evidence-based medicine is not easy. Some difficulties are obvious, such as the difficulty to mount a powerful random prospective controlled study. This article, however, will deal with 2 types of not-so-obvious, difficulties that plague clinicians who advocate evidence-based medicine. The first type has to do with our knowledge base. We tend to think of our knowledge base as being a collection of facts that represent absolute truth and are completely dependable now and will be for the future. It is more likely that these facts are better thought of as beliefs that are fragile and about which we should be skeptical. The second type of difficulty has to do with the human brain and its ability to reach valid decisions. Let us first consider difficulties with establishing good outcome measures that are essential for good evidence.