Are systematic reviews and meta-analyses still useful research? Yes

Excerpt

Systematic reviews (SR) are commonly defined as “a summary of studies addressing a clear question, using systematic and explicit methods to identify, select, and critically appraise relevant studies, and to collect and analyse data from them” [1]. One of the essential tenets of evidence-based medicine is that optimal care requires up-to-date, rigorous summaries of evidence [2]. Without such summaries, clinicians and patients are vulnerable to unrepresentative samples of the evidence, misinterpreted and biased estimates of benefits and harms of interventions. For instance, consider the evolution of expert views regarding thrombolysis for acute myocardial infarction (AMI) [3]. An SR found 33 trials evaluating streptokinase in AMI patients, 25 suggesting mortality reduction and six reaching conventional levels of statistical significance. A cumulative meta-analysis found that by 1973—after eight trials (2432 patients)—results showed a mortality reduction with streptokinase. None of the subsequent trials changed the direction or magnitude of the odds ratio of dying. Yet, 34,542 AMI patients continued to be exposed to placebo in subsequent trials, including so-called mega-trials. The reason for the conduct of all the unnecessary trials was that experts, without the benefit of an SR and meta-analyses, could not grasp the big picture of the benefits of thrombolytic therapy, forcing trialists to conduct study after study until the message finally got through. In the meanwhile, patients died unnecessarily. …