title: Treatment compliance and effectiveness of a cognitive behavioural intervention for low back pain: a complier average causal effect approach to the BeST data set.
abstract: BACKGROUND
  Group cognitive behavioural intervention (CBI) is effective in reducing low-back pain and disability in comparison to advice in primary care. The aim of this analysis was to investigate the impact of compliance on estimates of treatment effect and to identify factors associated with compliance.
  
  
  METHODS
  In this multicentre trial, 701 adults with troublesome sub-acute or chronic low-back pain were recruited from 56 general practices. Participants were randomised to advice (control n = 233) or advice plus CBI (n = 468). Compliance was specified a priori as attending a minimum of three group sessions and the individual assessment. We estimated the complier average causal effect (CACE) of treatment.
  
  
  RESULTS
  Comparison of the CACE estimate of the mean treatment difference to the intention-to-treat (ITT) estimate at 12 months showed a greater benefit of CBI amongst participants compliant with treatment on the Roland Morris Questionnaire (CACE: 1.6 points, 95% CI 0.51 to 2.74; ITT: 1.3 points, 95% CI 0.55 to 2.07), the Modified Von Korff disability score (CACE: 12.1 points, 95% CI 6.07 to 18.17; ITT: 8.6 points, 95% CI 4.58 to 12.64) and the Modified von Korff pain score (CACE: 10.4 points, 95% CI 4.64 to 16.10; ITT: 7.0 points, 95% CI 3.26 to 10.74). People who were non-compliant were younger and had higher pain scores at randomisation.
  
  
  CONCLUSIONS
  Treatment compliance is important in the effectiveness of group CBI. Younger people and those with more pain are at greater risk of non-compliance.
  
  
  BACKGROUND
  Current Controlled Trials ISRCTN54717854.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Knox
authors.forename: Ranjit
authors.initials: R
authors.lastname: Lall
authors.forename: Zara
authors.initials: Z
authors.lastname: Hansen
authors.affiliation: Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry CV7 1AL, UK. sarah.lamb@ndorms.ox.ac.uk.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Lamb
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D015928:Cognitive Behavioral Therapy; D004185:Disability Evaluation; D005260:Female; D006126:Group Processes; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D057194:Intention to Treat Analysis; D017116:Low Back Pain / Q000175:diagnosis / Q000523:psychology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D010349:Patient Compliance; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013997:Time Factors; D016896:Treatment Outcome; D006113:United Kingdom