Validity of Meta-analysis in Diabetes: We Need to Be Aware of Its Limitations

To deliver high-quality clinical care to patients with diabetes and other chronic conditions, clinicians must understand the evidence available from studies that have been performed to address important clinical management questions. In an evidence-based approach to clinical care, the evidence from clinical research should be integrated with clinical expertise, pathophysiological knowledge, and an understanding of patient values. As such, in an effort to provide information from many studies, the publication of diabetes meta-analyses has increased markedly in the recent past, using either observational or clinical trial data. In this regard, guidelines have been developed to direct the performance of meta-analysis to provide consistency among contributions. Thus, when done appropriately, meta-analysis can provide estimates from clinically and statistically homogeneous but underpowered studies and is useful in supporting clinical decisions, guidelines, and cost-effectiveness analysis. However, often these conditions are not met, the data considered are unreliable, and the results should not be assumed to be any more valid than the data underlying the included studies. To provide an understanding of both sides of the argument, we provide a discussion of this topic as part of this two-part point-counterpoint narrative. In the point narrative as presented below, Dr. Home provides his opinion and review of the data to date showing that we need to carefully evaluate meta-analyses and to learn what results are reliable. In the counterpoint narrative following Dr. Home’s contribution, Drs. Golden and Bass emphasize that an effective system exists to guide meta-analysis and that rigorously conducted, high-quality systematic reviews and meta-analyses are an indispensable tool in evidence synthesis despite their limitations. —William T. Cefalu, MD Editor in Chief, Diabetes Care