What meta-analyses teach us: pros and cons

The exponential increase in publications focusing on important clinical issues represents a major challenge for patients, physicians, and decision-makers, despite the braggadocio of many experts. Meta-analysis, when conducted within the context of a systematic review, offers an efficient and potent tool to summarize the clinical evidence accrued on a specific clinical question. Despite their many strengths, which include statistical precision, external validity, and the opportunity to analyze subgroups and moderators, meta-analyses also have many limitations. In addition, they are criticized because potentially an exercise in "mega-silliness", mixing "apples and oranges", unable to improve the quality of primary studies (in keeping with the say "garbage in-garbage out"), and focusing on an "average patient" who is only hypothetical. Yet, it is evident that meta-analyses will continue to play a key role in informing decision making whenever the best approach is not self-evident. Thus, it is mandatory to know their main features in order to use them critically and constructively, without being dominated nor scared.