Systematic Review

A systematic review is a structured summary of all the research on a defined question, using a written plan to search for studies, decide which ones count, judge their quality and draw conclusions. It is designed to be more complete and less biased than a traditional review in which an author picks the studies to discuss.

Origin

Systematic reviews grew out of the evidence-based medicine movement of the 1970s through 1990s; the Cochrane Collaboration, founded in 1993, made them a standard tool. Government agencies later adopted similar methods for evaluating chemical hazards, including for asbestos.

Significance in Asbestos Context

Systematic reviews sit near the top of the usual hierarchy of medical evidence, and regulators rely on them. Bodies such as IARC review the full body of research before classifying a substance, and the U.S. EPA used systematic-review methods in its risk evaluation of chrysotile asbestos under TSCA. In litigation, experts are often asked whether they reviewed the literature systematically or picked studies that support their opinion; courts applying the Daubert standard may consider whether an expert's method was reliable, and a selective review can be attacked as cherry-picking. A systematic review may or may not include a meta-analysis, which is the statistical combining of results. Reviews also vary in quality, and the conclusions depend on the question asked and the rules for including studies. For families, knowing that a conclusion comes from a systematic review, rather than a single study, helps judge how much weight it deserves.

Example Sentence

The plaintiff's expert based her opinion on a systematic review of studies of brake mechanics, explaining how she searched for and selected each study.

Related Terms

Meta-Analysis, Epidemiology, IARC Classification, TSCA Risk Evaluation, Daubert Standard, Bradford Hill Criteria, General Causation

Notes

• A conclusion based on a systematic review usually carries more weight than one based on a single study.
• Ask whether an expert's review followed a written search plan or was based on selected studies.