A couple of the nasties lurking in evidence-based medicine

The Evidence-Based Medicine (EBM) movement is an ideological force in health research and health policy which asks for allegiance to two types of methodological doctrine. The first is the highly quotable motherhood statement: for example, that we should make conscientious, explicit and judicious use of current best evidence (paraphrasing Sackett). The second type of doctrine, vastly more specific and in practice more important, is the detailed methodology of design and analysis of experiments. This type of detailed methodological doctrine tends to be simplified by commentators but followed to the letter by practitioners. A number of interestingly dumb claims have become entrenched in prominent versions of these more specific methodological doctrines. I look at just a couple of example claims, namely: Any randomised controlled trial (RCT) gives us better evidence than any other study. Confidence intervals are always useful summaries of at least part of the evidence an experiment gives us about a hypothesis. To offer a positive doctrine which might move us past the current conflict of micro-theories of evidence, I propose a mild methodological pluralism: in any local context in which none of a variety of scientific methodologies is clearly and uncontentiously right, researchers should not be discouraged from using any methodology for which they can provide a good argument.