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Potential Pitfalls of Reporting and Bias in Observational Studies With Propensity Score Analysis Assessing a Surgical Procedure: A Methodological Systematic Review

Lonjon, Guillaume MD*,†,‡; Porcher, Raphael PhD*,‡,§; Ergina, Patrick MD; Fouet, Mathilde MD*,‡; Boutron, Isabelle PhD*,‡,§

doi: 10.1097/SLA.0000000000001797
Review Paper

Objective: To describe the evolution of the use and reporting of propensity score (PS) analysis in observational studies assessing a surgical procedure.

Background: Assessing surgery in randomized controlled trials raises several challenges. Observational studies with PS analysis are a robust alternative for comparative effectiveness research.

Methods: In this methodological systematic review, we identified all PubMed reports of observational studies with PS analysis that evaluated a surgical procedure and described the evolution of their use over time. Then, we selected a sample of articles published from August 2013 to July 2014 and systematically appraised the quality of reporting and potential bias of the PS analysis used.

Results: We selected 652 reports of observational studies with PS analysis. The publications increased over time, from 1 report in 1987 to 198 in 2013. Among the 129 reports assessed, 20% (n = 24) did not detail the covariates included in the PS and 77% (n = 100) did not report a justification for including these covariates in the PS. The rate of missing data for potential covariates was reported in 9% of articles. When a crossover by conversion was possible, only 14% of reports (n = 12) mentioned this issue. For matched analysis, 10% of articles reported all 4 key elements that allow for reproducibility of a PS-matched analysis (matching ratio, method to choose the nearest neighbors, replacement and method for statistical analysis).

Conclusions: Observational studies with PS analysis in surgery are increasing in frequency, but specific methodological issues and weaknesses in reporting exist.

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*INSERM, UMR 1153, Centre of Research in Epidemiology and Statistics Sorbonne Paris Cité (CRESS), METHODS Team, Paris, France

Orthopaedic Department, Assistance Publique-Hôpitaux de Paris, European Hospital Georges Pompidou, Paris, France

Medical school, Paris Descartes university, Sorbonne Paris cité, Paris, France

§Centre of research in epidemiology and statistics Sorbonne Paris Cité , Hopital Hotel dieu, place du Parvis notre dame, Paris, France

Department of Surgery, McGill University Health Centre, Montreal, Canada.

Reprints: Guillaume Lonjon, MD, INSERM, UMR 1153, Centre of Research in Epidemiology and Statistics Sorbonne Paris Cité (CRESS), METHODS team, Paris, France. E-mail:

Disclosure: The authors report no conflicts of interest.

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