Meta-Analysis in Clinical Research: An Overview of the Statistics of Evidence Synthesis

Pediatric research is often faced with ethical and logistical challenges. Pediatric literature is dominated by studies that are performed to answer similar questions but of small sample size, varying in methodology, results, and conclusions. Therefore, evidence synthesis methods are necessary for summarizing existing evidence and recognizing gaps in knowledge. A systematic review is used to summarize evidence in conjunction with meta-analysis, a statistical technique that combines results from studies to generate a summary estimate with CIs. Systematic reviews with meta-analysis represent the highest level in the hierarchy of evidence to inform clinical practice. Meta-analysis, by combining studies, increases precision and may help determine certainty of evidence for a specific clinical question. Systematic reviews and meta-analyses allow the clinician to explore reasons for variability and heterogeneity. Based on the intended research question, several types of meta-analysis are available, which must be chosen appropriately. We review the principles and types of meta-analyses that are used to summarize clinical evidence. We also summarize the common strengths (eg, increasing precision) and limitations (eg, publication bias and study heterogeneity) of a meta-analysis. Our review will inform clinicians on appraising published meta-analyses and may equip them with a framework and methods to perform their own.