Abstract
Introduction
The STarT Back trial demonstrated that targeting back pain treatment according to patient prognosis (low, medium or high-risk subgroups) is effective. However, the mechanisms leading to these improved treatment outcomes remain unknown. This study aimed to identify which psychological variables included in the study were mediating treatment outcome for all patients and within the low, medium and high-risk subgroups.
Methods
Secondary analysis was conducted on 466 patients randomised to the active treatment arm with 4-month follow-up available. Psychological variables included depression (HADs), fear (TSK), catastrophising (PCS), bothersomeness and illness perception constructs (IPQ brief) e.g. personal control. Treatment outcome was characterised using change in disability score (RMDQ) at 4-months. Residualised change scores were calculated for each variable and Pearson's correlations were calculated overall and at the subgroup level to determine potential mediating variables for disability improvement.
Results
Overall, correlations with RMDQ change were .62 for change in bothersomeness, .56 for change in catastrophising, .51 for change in fear, .48 for change in anxiety, .58 for change in depression, −.32 for change in personal control and .40 for change in symptom identity. The strength of correlation generally increased from low to high-risk subgroups, e.g. bothersomeness (low=.54, high=.70). However, the predominant variables mediating treatment outcome were common across risk-groups.
Conclusion
The psychological variables which were highly correlated with improvements in disability were bothersomeness, depression and catastrophising. This finding was consistent across low, medium and high-risk subgroups. This study is ongoing and further mediation analysis using structural equation modelling is in progress.
Conflicts of Interest
None
Source of Funding
NIHR Spinal Pain Programme grant
