State of the evidence: current status and prospects of meta-analysis in infectious diseases.

Meta-analysis is increasingly applied in infectious diseases to summarize clinical data and to evaluate the strength, diversity, and deficiencies of evidence for medical questions of interest. We present an overview of the current status of meta-analysis in the area of infectious diseases and the lessons learnt from its applications. Recently published meta-analyses show that several important areas of research on infectious diseases lack sufficient randomized evidence. Often evidence is scattered across a large number of small trials, making meta-analysis a promising way to integrate diverse results. Quality of trials in the field is often poor. There are several examples where evidence was accumulated primarily for marketing rather than for scientific purposes. Finally, meta-analyses are also raising the problem of what constitutes clinically significant treatment benefits, as well as interesting issues about the reproducibility of clinical evidence and its evolving nature. The increasing applications of meta-analytic methods in the study of infectious diseases may enhance data sharing and international collaborations.