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Open Access Research article

Treatment compliance and effectiveness of a cognitive behavioural intervention for low back pain: a complier average causal effect approach to the BeST data set

Christopher R Knox1, Ranjit Lall1, Zara Hansen1 and Sarah E Lamb12*

Author Affiliations

1 Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry CV7 1AL, UK

2 Nuffield Department of Orthopaedics, Kadoorie Critical Care Research Centre, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford OX3 9DU, UK

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BMC Musculoskeletal Disorders 2014, 15:17  doi:10.1186/1471-2474-15-17

Published: 14 January 2014

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 nā€‰=ā€‰233) or advice plus CBI (nā€‰=ā€‰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.

Trial registration

Current Controlled Trials ISRCTN54717854

Keywords:
Compliance; CACE analysis; Low back pain; Cognitive behaviour therapy