Users' Guide to the Surgical Literature. Case-control Studies in Surgical Journals

Introduction: Some articles in surgical journals identify themselves as case-control studies, but their methods differ substantially from conventional epidemiologic case-control study (ECC) designs. Most of these studies appear instead to be retrospective cohort studies or comparisons of case series.

Methods: We identified all self-identified "case-control" studies published between 1995 and 2000 in 6 surgical journals, to determine the proportion that were true ECCs and to identify study characteristics associated with being true ECCs.

Results: Only 19 out of 55 articles (35%) described true ECCs. More likely to be ECCs were those articles that reported "odds ratios" (ORs) (the OR for being an ECC if a study reported "ORs" compared with those reporting no "ORs" 15.3; 95% confidence interval [CI] 2.8-82.6) and whose methods included logistic regression analysis (OR 3.6, CI 1.0-12.9). Studies that focused on the evaluation of a surgical procedure were less likely to be ECCs (OR 0.2, CI 0.1-0.7) than other types of studies, such as those focusing on risk factors for disease.

Conclusions: The term "case-control study" is frequently misused in the surgical literature.