The influence of psychosocial variables on treatment outcomes, expectations and costs in acute low back pain

Low back pain (LBP) is a common and costly problem. Among the top primary care research priorities are identifying prognostic subgroups of patients with LBP and identifying specific management strategies based on relevant subgroups. The Start Back Screening Tool (SBST) is a primary care decision tool that stratifies patients into prognostic subgroups based on the patient's risk for prolonged disability. Other subgrouping strategies screen for patients who fit a prediction rule (CPR) that may identify them as likely to respond to spinal manipulation (SM). It is unclear whether patients who are stratified by the SBST (high- and medium-risk) and who meet a CPR respond differentially to SM with exercise based on their risk stratification. In a secondary analysis of a randomized controlled trial, we found no 2-way interactions between risk stratification and treatment group at 4-week, 3-month or 1-year time points for disability or pain, indicating that the effects of treatment were no different between the medium- and high-risk groups. When we examined the effects of treatment separately within each risk subgroup, SM with exercise was superior to usual care at 3 months for disability and pain in those categorized as high-risk (mean difference = 3.95, 95% CI: 0.02, 7.87). After controlling for covariates, the SBST accounted for 2.4% (β = 4.25, p = 0.035) of the variance in the 4-week disability. In the same group of patients, we explored the relationship between the SBST and treatment expectations. Expectations of benefit from ten commonly used interventions for LBP were represented by four principal components: Exercise, Passive, Rest/Medication and Surgery). There were no associations between the components and the SBST (high versus medium- and low-risk). Finally, we retrospectively examined the influence of a mental health (MH) comorbidity on LBP-related healthcare costs in new consulters to primary care for LBP. Interaction terms between mental health comorbidity and patient factors were explored as contributors to predicting total costs. Individuals with a comorbid MH condition had higher LBP-related costs than those without. Males with a MH comorbidity experienced greater LBP-related healthcare costs than females (mean difference = $1077.26 USD, 95% CI = 428.10 - 1776.43).