title: Impact of STROBE statement publication on quality of observational study reporting: interrupted time series versus before-after analysis.
abstract: BACKGROUND
  In uncontrolled before-after studies, CONSORT was shown to improve the reporting of randomised trials. Before-after studies ignore underlying secular trends and may overestimate the impact of interventions. Our aim was to assess the impact of the 2007 STROBE statement publication on the quality of observational study reporting, using both uncontrolled before-after analyses and interrupted time series.
  
  
  METHODS
  For this quasi-experimental study, original articles reporting cohort, case-control, and cross-sectional studies published between 2004 and 2010 in the four dermatological journals having the highest 5-year impact factors (≥ 4) were selected. We compared the proportions of STROBE items (STROBE score) adequately reported in each article during three periods, two pre STROBE period (2004-2005 and 2006-2007) and one post STROBE period (2008-2010). Segmented regression analysis of interrupted time series was also performed.
  
  
  RESULTS
  Of the 456 included articles, 187 (41%) reported cohort studies, 166 (36.4%) cross-sectional studies, and 103 (22.6%) case-control studies. The median STROBE score was 57% (range, 18%-98%). Before-after analysis evidenced significant STROBE score increases between the two pre-STROBE periods and between the earliest pre-STROBE period and the post-STROBE period (median score2004-05 48% versus median score2008-10 58%, p<0.001) but not between the immediate pre-STROBE period and the post-STROBE period (median score2006-07 58% versus median score2008-10 58%, p = 0.42). In the pre STROBE period, the six-monthly mean STROBE score increased significantly, by 1.19% per six-month period (absolute increase 95%CI, 0.26% to 2.11%, p = 0.016). By segmented analysis, no significant changes in STROBE score trends occurred (-0.40%; 95%CI, -2.20 to 1.41; p = 0.64) in the post STROBE statement publication.
  
  
  CONCLUSIONS
  The quality of reports increased over time but was not affected by STROBE. Our findings raise concerns about the relevance of uncontrolled before-after analysis for estimating the impact of guidelines.
authors.affiliation: Université Paris Est Créteil (UPEC), LIC EA4393 (Laboratoire d'Investigation Clinique), Créteil, France ; AP-HP, Hôpital Henri-Mondor, Department of Clinical Research and Public Health, Créteil, France ; AP-HP, Hôpital Henri-Mondor, Unité de Recherche Clinique (URC), Créteil, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Bastuji-Garin
authors.forename: Emilie
authors.initials: E
authors.lastname: Sbidian
authors.forename: Caroline
authors.initials: C
authors.lastname: Gaudy-Marqueste
authors.forename: Emilie
authors.initials: E
authors.lastname: Ferrat
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Roujeau
authors.forename: Marie-Aleth
authors.initials: MA
authors.lastname: Richard
authors.forename: Florence
authors.initials: F
authors.lastname: Canoui-Poitrine
mesh_terms: D000043:Abstracting and Indexing; D015706:Bibliometrics; D016022:Case-Control Studies; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003880:Dermatology / Q000379:methods; D064887:Observational Studies as Topic; D011643:Publishing / Q000592:standards*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012107:Research Design; D013997:Time Factors