title: Rationale for unequal randomization in clinical trials is rarely reported: a systematic review.
abstract: OBJECTIVE
  To assess the reporting of the unequal randomization ratio in reports of trials with this design and to identify the justification for the design.
  
  
  METHODS
  Systematic review of reports of trials with unequal randomization. We selected all original reports of two parallel-group randomized controlled trials with unequal randomization, which were published in 2009 and 2010 in core clinical journals in MEDLINE on the basis of the abstract (and full text, if necessary). Additional information was collected by an author survey.
  
  
  RESULTS
  We retrieved 106 reports (prevalence, 4.7%). The randomization ratio was not stated in 8.5% of reports and 51.9% of abstracts. Sample size calculation was reported in 70 reports, with unequal randomization not taken into account in 25.7% (n = 18). Justification for unequal randomization was not reported in 77.4% (n = 82) of reports. Combining information from reports and author surveys, we had justification for 41 trials. The main justification was safety issues for 20 trials. In 11 of those latter 20 reports, adverse events were not fully reported.
  
  
  CONCLUSIONS
  A better reporting of the randomization ratio, sample size calculation, and justification to unequal randomization could help readers appraise the quality and risk of bias of such trials.
authors.affiliation: INSERM UMR 1153, Epidemilogy ans statistics Sorbonne Paris Cité, 1 place du Parvis Notre Dame, 75181 Paris, France; INSERM CIC 1415, 2 boulevard Tonnelé, 37044 Tours cedex 9, France; Université François-Rabelais de Tours, faculté de médecine, 10 boulevard Tonnelé, 37000 Tours, France; Département Universitaire de Médecine Générale, Faculté de Médecine - Université François-Rabelais de Tours, PRES Centre-Val de Loire Université, 10 Boulevard Tonnellé, B.P. 3223, 37032 Tours Cedex 1, France. Electronic address: clarisse.dibao-dina@univ-tours.fr.
authors.forename: Clarisse
authors.initials: C
authors.lastname: Dibao-Dina
authors.affiliation: INSERM UMR 1153, Epidemilogy ans statistics Sorbonne Paris Cité, 1 place du Parvis Notre Dame, 75181 Paris, France; INSERM CIC 1415, 2 boulevard Tonnelé, 37044 Tours cedex 9, France; Université François-Rabelais de Tours, faculté de médecine, 10 boulevard Tonnelé, 37000 Tours, France; CHRU de Tours, 2 boulevard Tonnelé, 37044 Tours cedex 9, France.
authors.forename: Agnès
authors.initials: A
authors.lastname: Caille
authors.affiliation: INSERM UMR 1153, Epidemilogy ans statistics Sorbonne Paris Cité, 1 place du Parvis Notre Dame, 75181 Paris, France; INSERM CIC 1415, 2 boulevard Tonnelé, 37044 Tours cedex 9, France; Université François-Rabelais de Tours, faculté de médecine, 10 boulevard Tonnelé, 37000 Tours, France; CHRU de Tours, 2 boulevard Tonnelé, 37044 Tours cedex 9, France.
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Sautenet
authors.affiliation: INSERM CIC 1415, 2 boulevard Tonnelé, 37044 Tours cedex 9, France; CHRU de Tours, 2 boulevard Tonnelé, 37044 Tours cedex 9, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Chazelle
authors.affiliation: INSERM UMR 1153, Epidemilogy ans statistics Sorbonne Paris Cité, 1 place du Parvis Notre Dame, 75181 Paris, France; INSERM CIC 1415, 2 boulevard Tonnelé, 37044 Tours cedex 9, France; Université François-Rabelais de Tours, faculté de médecine, 10 boulevard Tonnelé, 37000 Tours, France; CHRU de Tours, 2 boulevard Tonnelé, 37044 Tours cedex 9, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Giraudeau
mesh_terms: D006801:Humans; D011643:Publishing / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D018401:Sample Size
keywords: Justification; Randomization ratio; Randomized controlled trials; Reporting; Systematic review; Unequal randomization