Systematic review and meta-analysis: a critical examination of the methodology

Nowadays, the pyramid of evidence is the main model of decision-making for healthcare professionals. According to this concept, data from randomized clinical trials (RCTs) are considered lower in hierarchy than data obtained from systematic reviews (SRs) and meta-analyses (MAs). However, it (sic): is not established whether it is appropriate to rate large RCTs with hard endpoints lower than SRs and MAs that combine data from smaller RCTs of questionable quality, or even from prospective or retrospective observational studies. It is also important to consider that in addition to assessing the quality of the studies included in the SRs and MAs, it is necessary to assess the accuracy of the SRs and MAs themselves. If not rigorously conducted, they can also contain systematic errors, leading to increased risks of data manipulation. The publication covers the main stages and principles of preparing SRs and MAs, common types of systematic errors that can arise at each stage, and methods to minimize them. We believe that the tools, knowledge, and skills we offer will help practicing doctors and healthcare professionals critically assess the results obtained from SRs and MAs in terms of methodology and the mitigation of potential data manipulation risks.