title: A systematic review finds variable use of the intention-to-treat principle in musculoskeletal randomized controlled trials with missing data.
abstract: OBJECTIVE
  In randomized trials, the primary analysis should be consistent with the intention-to-treat (ITT) principle and should address missing data appropriately to draw valid inferences. This review focuses on current practices relating to the ITT principle and methods to handle missing data in the major musculoskeletal journals.
  
  
  METHODS
  A systematic review of randomized trials published in 2010 and 2011 in five musculoskeletal journals was performed.
  
  
  RESULTS
  We reviewed 91 trials: 38% performed a full ITT analysis (analyzing outcome data for all randomized participants) and 31% performed a partial ITT analysis (excluding participants with no follow-up data). The overall median dropout was 12%; 60% of trials had more than 10% dropouts, and 32% of trials had more than 20% dropouts. Among those that performed an ITT analysis, the majority adopted a form of single imputation; last observation carried forward was the designated approach in most cases. Mixed models for repeated measures and/or multiple imputations were limited to eight trials.
  
  
  CONCLUSIONS
  It appears that many trials reporting missing data are inappropriately analyzed and may therefore be prone to biased estimates and invalid inferences.
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute of Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK.
authors.forename: Royes
authors.initials: R
authors.lastname: Joseph
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute of Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK.
authors.forename: Julius
authors.initials: J
authors.lastname: Sim
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute of Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK.
authors.forename: Reuben
authors.initials: R
authors.lastname: Ogollah
authors.affiliation: Arthritis Research UK Primary Care Centre, Research Institute of Primary Care and Health Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK. Electronic address: a.m.lewis@keele.ac.uk.
authors.forename: Martyn
authors.initials: M
authors.lastname: Lewis
mesh_terms: D003627:Data Interpretation, Statistical; D006801:Humans; D057194:Intention to Treat Analysis / Q000379:methods* / Q000706:statistics & numerical data; D009140:Musculoskeletal Diseases / Q000628:therapy; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D011642:Publications / Q000592:standards; D016032:Randomized Controlled Trials as Topic / Q000379:methods* / Q000706:statistics & numerical data
keywords: Dropout; Intention-to-treat; Missing data; Musculoskeletal conditions; Randomized controlled trial; Sensitivity analysis; Systematic review