Meta-analysis: pitfalls and hints.

The present work is an overview of the main pitfalls which may occur when a researcher performs a meta-analysis. The main goal is to help clinicians evaluate published research results. Organizing and carrying out a meta-analysis is hard work, but the findings can be significant. Meta-analysis is a powerful tool to cumulate and summarize the knowledge in a research field, and to identify the overall measure of a treatment's effect by combining several conclusions. However, it is a controversial tool, because even small violations of  certain rules can lead to misleading conclusions. In fact, several decisions made when designing and performing a meta-analysis require personal judgment and expertise, thus creating personal biases or expectations that may influence the result. Meta-analysis' conclusions should be interpreted in the light of various checks, discussed in this work, which can inform the readers of the likely reliability of the conclusions. Specifically, we explore the principal steps (from writing a prospective protocol of analysis to results' interpretation) in order to minimize the risk of conducting a mediocre meta-analysis and to support researchers to accurately evaluate the published findings.