title: Case-control studies in diabetes. Do they really use a case-control design?
abstract: OBJECTIVE
  Studies defined as case-control do not always use this design. We aimed to estimate the frequency of mislabelled case-control studies in published articles in the area of diabetes and to identify the predictors of incorrect labelling.
  
  
  METHODS
  We searched Medline and Web of Science for articles with "diabetes" and "case control" in title and filtered for language (English/Romance) and period (January 2010-December 2014). Inclusion criteria were: (1) statement to use a case-control design in title, (2) to be a final full-length publication and (3) to have original data in the area of diabetes. Three independent reviewers went through titles, looked for full texts and reviewed them. Discrepancies were settled with a fourth reviewer. Expert epidemiologist advice was requested in case of doubt.
  
  
  METHODS
  case-control mislabelling; addressed predictors: publication year, journal impact factor and journal subject.
  
  
  METHODS
  proportion of mislabelled CC articles and assessment of predictors by multivariate logistic regression analysis.
  
  
  RESULTS
  We retrieved 362 articles, 251 of them fulfilling inclusion criteria. The proportion of mislabelled CC studies was 43.8% (confidence interval 95% 37.7-50.0%). Most mislabelled studies had a cross-sectional design (82.7%). Predictors of mislabelling were publication year, journal impact factor and journal area.
  
  
  CONCLUSIONS
  A relevant subset of studies defined as case-control in the area of diabetes correspond to mislabelled cross-sectional studies. Incorrect labelling misleads readers regarding the interpretation of results and the cause-effect hypothesis. Researchers, reviewers and editors should be aware of and commit to settle this issue.
authors.affiliation: Servei d'Endocrinologia i Nutrició, Hospital de la Santa Creu i Sant Pau, Sant Antoni Mª Claret, 167, 08025, Barcelona, Spain.
authors.forename: Analía
authors.initials: A
authors.lastname: Ramos
authors.affiliation: Servei d'Endocrinologia i Nutrició, Hospital de la Santa Creu i Sant Pau, Sant Antoni Mª Claret, 167, 08025, Barcelona, Spain.
authors.forename: Lilian Cristina
authors.initials: LC
authors.lastname: Mendoza
authors.affiliation: Servei d'Endocrinologia i Nutrició, Hospital de la Santa Creu i Sant Pau, Sant Antoni Mª Claret, 167, 08025, Barcelona, Spain.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Rabasa
authors.affiliation: Department of Clinical Epidemiology and Public Health, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.|Institut d'Investigació Biomédica Sant Pau (IIB Sant Pau), Barcelona, Spain.|Department of Pediatrics, Obstetrics and Gynecology an Preventive Medicine, Universitat Autònoma de Barcelona, Bellaterra, Spain.|CIBER Epidemiología y Salud Pública (CIBERESP), Madrid, Spain.
authors.forename: Ignasi
authors.initials: I
authors.lastname: Bolíbar
authors.affiliation: Department of Clinical Epidemiology and Public Health, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.|Institut d'Investigació Biomédica Sant Pau (IIB Sant Pau), Barcelona, Spain.|Department of Pediatrics, Obstetrics and Gynecology an Preventive Medicine, Universitat Autònoma de Barcelona, Bellaterra, Spain.|Red de investigación Cardiovascular (RIC), Madrid, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Puig
authors.affiliation: Servei d'Endocrinologia i Nutrició, Hospital de la Santa Creu i Sant Pau, Sant Antoni Mª Claret, 167, 08025, Barcelona, Spain. rcorcoy@santpau.cat.|Institut d'Investigació Biomédica Sant Pau (IIB Sant Pau), Barcelona, Spain. rcorcoy@santpau.cat.|Departament of Medicine, Universitat Autònoma de Barcelona, Bellaterra, Spain. rcorcoy@santpau.cat.|Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Madrid, Spain. rcorcoy@santpau.cat.
authors.forename: Rosa
authors.identifier: http://orcid.org/0000-0001-5055-6814
authors.initials: R
authors.lastname: Corcoy
mesh_terms: D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000453:epidemiology*; D015340:Epidemiologic Research Design; D006801:Humans; D055811:Journal Impact Factor; D016239:MEDLINE; D009626:Terminology as Topic
keywords: Case–control studies; Mislabelling; Study design