Common pitfalls in the conduct of clinical research.

Recently, paradigm shift from expert opinion towards evidence-based medicine has occurred encouraging physicians to base their treatment decisions on the best available research evidence. In the hierarchy of evidence randomized clinical trials (level 1 evidence) are considered of the highest quality (least biased) while non-randomized studies represent lower levels (levels 2-4). Several pitfalls in the design and conduct of clinical research include: lack of randomization, lack of concealment, lack of blinding, and errors in hypothesis testing (type I and II errors). A basic understanding of these principles of research will empower both investigators and readers when applying the results of research to clinical practice.