title: The choice of controls for providing validity and evidence in clinical research.
abstract: BACKGROUND
  Selection of controls, a group of subjects who are identical to the treatment group in all aspects that affect the outcome except the intervention of interest, is a significant criterion for conducting a study in evidence-based medical research. Few studies emphasize the appropriate selection of control groups in the plastic surgery literature.
  
  
  METHODS
  The authors performed a literature search in Plastic and Reconstructive Surgery from January 1, 2010, through December 31, 2011, for studies in which controls were needed. The number of studies using a control group, control selection criteria, and the characteristics of the control populations were evaluated.
  
  
  RESULTS
  Three hundred twenty-seven articles were obtained from our search using the keywords "case control studies" and "retrospective cohort studies." Among these studies, 121 articles were studies conducted in humans. All of these studies based on the study design required a control group, yet only 63 studies (52 percent) had a comparative control group. Of these studies, the authors found biases regarding the choice of controls, including selection bias, misclassification bias, and chronology bias.
  
  
  CONCLUSIONS
  The authors' review shows that 48 percent of the studies published in Plastic and Reconstructive Surgery that were required to have a control group failed to incorporate a well-defined control group. Specific details pertaining to the methods used and the success obtained with those methods in recruiting controls need to be stated explicitly in the article to ensure uniformity and to support the validity of the research.
authors.affiliation: Ann Arbor, Mich. From the Section of Plastic Surgery, Department of Surgery, University of Michigan Health System, and the Section of Plastic Surgery, University of Michigan Medical School.
authors.forename: Sunitha
authors.initials: S
authors.lastname: Malay
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Chung
mesh_terms: D035843:Biomedical Research; D016022:Case-Control Studies; D035061:Control Groups; D005260:Female; D006801:Humans; D008297:Male; D018579:Patient Selection; D019651:Plastic Surgery Procedures / Q000379:methods*; D012016:Reference Values; D015203:Reproducibility of Results; D012107:Research Design