Propensity-matched Comparison Between Chronic Nonspecific Low Back Pain and Axial Spondyloarthritis: Impact on patient-perceived Quality of Life

Prospective study. OBJECTIVE. To compare the burden between chronic nonspecific low back pain (LBP) and axial spondyloarthropathy (SpA). SUMMARY OF BACKGROUND DATA. Chronic nonspecific LBP and SpA are two debilitating yet different chronic musculoskeletal disorders. To compare their burden, propensity score matching is used to control for potential confounders and match the study subjects. MATERIALS AND METHODS. Two prospectively collected cohorts of LBP (n=269) and SpA (n=218) patients were studied. Outcomes included current LBP, 36-item Short Form Questionnaire, Oswestry Disability Index, EuroQol 5-dimension 5-level Questionnaire, and EuroQol Visual Analog Scale. With the inherent differences between the two types of patients, propensity score matching was performed for comparing the two groups. Baseline covariates of age, sex, education level, occupation, smoking, and drinking history were selected for the estimation of propensity scores for each subject with the logistic regression model. Significant independent variables for the outcome of current back pain were included in the multivariate logistic regressions. RESULTS. A total of 127 matched pairs were identified, with 254 patients. In the matched cohort, more patients with chronic LBP had current back pain (95.3%) as compared with SpA (71.7%). Patients with SpA were younger (P<0.001), with more males (P<0.001), and better educated (P=0.001). There was less current back pain and higher nonsteroidal anti-inflammatory drug use (P<0.001). Most SpA patients had lower Oswestry Disability Index than LBP patients and with low disease activity. Patients with LBP had worse outcome scores as compared with SpA patients given the same Visual Analog Scale. LBP patients had 8.6 times the odds (95% CI: 3.341–20.671; P<0.001) of experiencing current back pain compared with SpA patients. CONCLUSIONS. The disease activity of SpA patients is well controlled. However, patients with chronic LBP have worse pain severity, disability, and health-related quality of life. This has implications on resource utilization and the necessity of advancing LBP understanding and management. LEVEL OF EVIDENCE. Type I prognostic study.