The UK back pain subpopulation study: Predictors of outcome in patients receiving chiropractic treatment

Abstract

Introduction: Non-specific low back pain is a common condition that continues to place a considerable burden on society. Various treatment approaches have emerged which are aimed at targeting non-specific low back pain and one of the most commonly recommended of these is spinal manipulative therapy, which is a central component of the chiropractic approach. However, despite observations in clinical practice in which some individuals respond well, results from clinical trials of treatment interventions for low back pain, such as chiropractic, are repeatedly seen to have small effect sizes. A plausible explanation for this is that low back pain may be considered a heterogeneous condition consisting of a number of subgroups of patients. Previously highlighted as a research priority, these subgroups and their predictive factors for outcome are beginning to be identified among low back pain patients receiving chiropractic treatment; however they are largely unstudied in the UK chiropractic patient population. The overall aim of this prospective cohort study was to attempt to identify predictors of outcomes in the short, medium and long term in low back pain patients undergoing chiropractic treatment in primary care settings throughout the UK. Methods: All practising members of the British Chiropractic Association were invited to participate in the study. Each chiropractor was required to recruit 10 consecutive low back pain patients. Patients were eligible for inclusion if they were between 18 and 60 years of age; presenting with a new episode of low back pain with or without leg pain; no treatment for low back pain within the previous 3 months; not pregnant; no contraindications to chiropractic care; a mobile phone user. All participating patients completed an informed consent form. Data were recorded utilising self report paper questionnaires by patients and chiropractors at baseline; and by patients only at the 4th visit, 3 months and 6 months follow-up. In addition, outcomes in the immediate short term were recorded from patients via text message on a daily basis for 7 days following the 1st visit. Baseline potential predictor variables encompassed demographics, clinical characteristic, clinical examination findings, work-related factors and psychosocial factors. The primary outcome was patient self-report global improvement. Patients were subgrouped according to the duration of the current episode of low back pain into acute (less than 2 weeks) and subacute/chronic (2 weeks or greater). Multivariate logistic regression analysis was used to construct prognostic models for baseline and change score variables at each follow-up. Results: Sixty-five chiropractors and 452 low back pain patients (222 acute; 230 subacute/chronic) participated in the study. The loss to follow-up at 6 months was approximately 65%. Almost 60% of patients participated in the text message study and the response rate was high (96%). The acute patients reported higher pain and disability at baseline; however a greater proportion of these patients were categorised as improved at each follow-up. The greatest drop in pain scores occurred in the 1st week in both subgroups. Several baseline predictor variables were independently associated with improvement at follow-up; however these differed between the subgroups with the exception of the patient-practitioner relationship. Early changes in pain were independently associated with improvement for the acute and subacute/chronic patients in the short and medium term. The discriminative ability of the baseline and change score prognostic models varied from weak to acceptable. Conclusion: The investigation presented here contributes to the body of research concerning prognostic factors, specifically those in the immediate short term, in the UK chiropractic LBP patient population and for being the largest study of its kind to date in the UK. Furthermore, this study highlights the potential impact of the patientpractitioner relationship on outcome in low back pain patients receiving chiropractic care. Although several baseline variables predicted improvement at follow-up, the importance of early change as a prognostic indicator is emphasised.