title: A systematic review found that deviations from intention-to-treat are common in randomized trials and systematic reviews.
abstract: OBJECTIVE
  To describe the characteristics, and estimate the incidence, of trials included in systematic reviews deviating from the intention-to-treat (ITT) principle.
  
  
  METHODS
  A 5% random sample of reviews were selected (Medline 2006-2010). Trials from reviews were classified based on the ITT: (1) ITT trials (trials reporting standard ITT analyses); (2) modified ITT (mITT) trials (modified ITT; trials deviating from standard ITT); or (3) no ITT trials.
  
  
  RESULTS
  Of 222 reviews, 81 (36%) included at least one mITT trial. Reviews with mITT trials were more likely to contain trials that used placebo, that investigated drugs, and that reported favorable results. The incidence of reviews with mITT trial ranged from 29% (17/58) to 48% (23/48). Of the 2,349 trials, 597 (25.4%) were classified as ITT trials, 323 (13.8%) as mITT trials, and 1,429 (60.8%) as no ITT trials. The mITT trials were more likely to have reported exclusions compared to studies classified as ITT trials and to have received funding.
  
  
  CONCLUSIONS
  The reporting of the type of ITT may differ according to the clinical area and the type of intervention. Deviation from ITT in randomized controlled trials is a widespread phenomenon that significantly affects systematic reviews.
authors.affiliation: Health Planning Service, Regional Health Authority of Umbria, Via Mario Angeloni, 61, 06124 Perugia, Italy. Electronic address: iosief_a@yahoo.it.
authors.forename: Iosief
authors.initials: I
authors.lastname: Abraha
authors.affiliation: Health Planning Service, Regional Health Authority of Umbria, Via Mario Angeloni, 61, 06124 Perugia, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Cozzolino
authors.affiliation: Health Planning Service, Regional Health Authority of Umbria, Via Mario Angeloni, 61, 06124 Perugia, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Orso
authors.affiliation: Transfusion Medicine Service, Azienda Ospedaliera di Perugia, Piazzale Menghini, 1, Perugia 06129, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Marchesi
authors.affiliation: Transfusion Medicine Service, Azienda Ospedaliera di Perugia, Piazzale Menghini, 1, Perugia 06129, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Germani
authors.affiliation: Surgical and Biomedical Sciences, University of Perugia, Piazzale Gambuli, 1, Perugia 06129, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Lombardo
authors.affiliation: Health Planning Service, Regional Health Authority of Umbria, Via Mario Angeloni, 61, 06124 Perugia, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Eusebi
authors.affiliation: General Medicine, Azienda USL Umbria 1, Via Guerriero Guerra, 21, Perugia 06127, Italy.
authors.forename: Rita
authors.initials: R
authors.lastname: De Florio
authors.affiliation: General Medicine, Azienda USL Umbria 2, Viale Donato Bramante, 37, Terni 05100, Italy.
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Luchetta
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, CRL 140, 1280 Main Street West, Hamilton, Ontario, Canada.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Iorio
authors.affiliation: Health Planning Service, Regional Health Authority of Umbria, Via Mario Angeloni, 61, 06124 Perugia, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Montedori
mesh_terms: D006801:Humans; D057194:Intention to Treat Analysis / Q000706:statistics & numerical data*; D016239:MEDLINE; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data; D012196:Review Literature as Topic
keywords: Bias; Deviation from intention-to-treat; Epidemiology; Meta-analysis; Modified intention-to-treat; Randomized trials