Relationship Between Pain Alleviation and Disease-specific Health-related Quality of Life Measures in Patients With Chronic Low Back Pain Receiving Duloxetine: Exploratory Post Hoc Analysis of a Japanese Phase 3 Randomized Study

This post hoc analysis of a Japanese phase 3 randomized study (ClinicalTrials.gov identifier: NCT01855919) investigated relationships between pain severity (assessed by the Brief Pain Inventory [BPI]) and disease-specific health-related quality of life (assessed by the 24-item Roland-Morris Disability Questionnaire [RDQ-24]) in duloxetine-treated patients with chronic low back pain (CLBP). METHODS: Patients with CLBP duration >6 months and BPI average score ≥4 received duloxetine 60 mg/d (N = 230) or placebo (N = 226) for 14 weeks. Spearman rank correlation coefficients were calculated for (1) BPI change from baseline and RDQ item change from baseline and (2) BPI change from baseline and the RDQ item baseline score in duloxetine-treated patients. RESULTS: Duloxetine treatment significantly improved the RDQ-24 total score compared with placebo; the greatest improvements were observed for RDQ02, RDQ17, and RDQ13. The strongest correlations between BPI change from baseline and RDQ item change from baseline were for RDQ13, RDQ23, and RDQ10. The correlation coefficients for the correlations between BPI change from baseline and the RDQ item baseline score were generally small. DISCUSSION: This post hoc analysis suggested that improvement in pain severity was associated with improvement in the RDQ-24 total score and in some individual RDQ items in duloxetine-treated patients with CLBP. Furthermore, positive responses to duloxetine in terms of the RDQ13, RDQ23, and RDQ10 items may correlate with better pain responses. CLINICAL TRIAL REGISTRY: The study described in this manuscript was registered at www.clinicaltrials.gov (NCT01855919).