Do baseline characteristics predict response to treatment for low back pain? Secondary analysis of the UK BEAM dataset [ISRCTN32683578]

Objectives. To identify characteristics of randomized controlled trial participants which predict greater benefits from physical treatments for low back pain. If successful, this would allow more appropriate selection of patients for different treatments. Methods. We did a secondary analysis of the UK Back pain Exercise And Manipulation trial (UK BEAM n=1334) dataset to identify baseline characteristics predicting response to manipulation, exercise and manipulation followed by exercise (combined treatment). Rather than simply identifying factors associated with overall outcome, we tested for the statistical significance of the interaction between treatment allocation, baseline characteristics and outcome to identify factors that predicted response to treatment. We also did a post-hoc subgroup analysis to present separate results for trial participants with subacute and chronic low back pain to inform future evidence synthesis. Results. Age, work status, age of leaving school, 'pain and disability', 'quality of life' and 'beliefs' at baseline all predicted overall outcome. None of these predicted response to treatment. In those allocated to combined treatment, there was a suggestion that expecting treatment to be helpful might improve outcome at 1 yr. Episode length at study entry did not predict response to treatment. Conclusion. Baseline participant characteristics did not predict response to the UK BEAM treatment packages. Using recognized prognostic variables to select patients for different treatment packages, without first demonstrating that these factors affect response to treatment, may be inappropriate. In particular, this analysis suggests that the distinction between subacute and chronic low back pain may not be useful when considering treatment choices.