When is a case-control study not a case-control study?

OBJECTIVE There is confusion in the rehabilitation literature about case-control studies because terms such as "cases" and "controls", used to refer to the subjects in the study, are confused with the design of the study. The aim of this study was to estimate the extent to which the label "case-control study" is misused in the rehabilitation literature and in the literature of other health disciplines. DESIGN A structured review revealed 7 rehabilitation journals, which, during the period 2000-2006, published 86 research articles in which the key word "case-control" or "case control" appeared in the title or abstract. For comparison purposes, other English language journals whose titles began with "Archives of" were also searched. RESULTS The proportion of mislabeled case-control studies in rehabilitation journals was 97% (83 of 86 studies were mislabeled). In contrast, 34% (76 of 221) of case-control studies published in the sample of non-rehabilitation journals were found to be mislabeled. The most frequent type of rehabilitation study misclassified as case-control was a cross-sectional study (56/86) followed by intervention studies (13/86). DISCUSSION The extent of mislabeling indicates that the case-control design is poorly understood by the rehabilitation community. This is not solely an issue of semantics; mislabeling led to misinterpretation of findings. CONCLUSION In rehabilitation, the research questions answered by case-control studies, regarding the etiology of health events, are rarely posed. Rehabilitation researchers must be attentive to issues of design and report correctly on design in publications.