Background/Purpose: Health-related quality of life (HRQOL) is decreased in individuals with chronic rheumatic diseases (CRD) yet remains undefined in adults with SAPHO syndrome and chronic nonbacterial osteomyelitis (SAPHO-CNO). We measured HRQOL with the EuroQol-5 Dimension instrument (EQ-5D-5L) and determined factors associated with HRQOL in adult SAPHO-CNO.

Methods: Adults with SAPHO-CNO (≥18 years of age) enrolled in the SAPHO-CNO study (SCS), a prospective longitudinal observational study, completed the EQ-5D-5L, a validated instrument for measuring HRQOL across five health dimensions, along with baseline questionnaires on demographics, clinical symptoms, disease activity, patient reported outcomes (PROs) and comorbidities. The EQ-5D value index reflects the subject’s health state profile, which can range from negative values (0=health state equivalent to dead) to 1 (full health). To model predictors of EQ-5D, variables were selected from literature review of HRQOL in CRDs, and SCS cohort characteristics (disease features, PROs, comorbidities, demographics). SAPHO-CNO disease features were inflammatory arthritis, spine involvement, skin rash, and total MSK symptom score (sum of painful and swollen skeletal areas in 42 regions; range 0-166). PROs were measured by the 21-point numeric rating scale (NRS, range 0-10) for patient-reported pain, function, and overall disease activity.  

Patient characteristics were summarized as medians (interquartile range) or proportions.  We performed bivariable analyses between each predictor and EQ-5D index with simple linear regression. We checked model assumptions and linearity by plotting. Next, multivariable linear regression (MLR) models were fit by multiple selection criteria (stepwise, forward, adjusted R², Mallow’s C_p) to identify best predictors of EQ-5D. We tested for inclusion of interaction terms, checked for collinearity, and evaluated overall model fit (i.e., plot residuals, inspect outliers). All analyses were performed using SAS (9.4).

Results: Baseline characteristics of 94 adults with SAPHO-CNO who were included in this cross-sectional analysis are summarized in Table 1. All explanatory variables were significantly associated with EQ-5D in bivariable analyses (p< 0.05). In MLR analyses, repeated modeling using alternative selection criteria determined that a three-variable model (Pain Score, Inflammatory Arthritis, Chronic Pain) provided the best fit (adjusted-R² = 0.53; p< .001). Due to collinearity of Pain and Function (rho=0.80), models were fit with Pain only. Thus, higher pain score, presence of inflammatory arthritis and chronic pain were significantly associated with a decrease in mean EQ-5D. Comparing standardized regression coefficients suggests that increases in pain score are associated with the largest decrease in EQ-5D (Table 2). 

Conclusion: We identified novel factors associated with decreased HRQOL in adults with SAPHO-CNO. Patient-reported pain or function, presence of inflammatory arthritis, and comorbid chronic pain should be addressed in the treatment of adults with SAPHO-CNO towards improving QOL.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/factors-associated-with-health-related-quality-of-life-in-adults-with-sapho-and-chronic-nonbacterial-osteomyelitis-a-cross-sectional-analysis-from-the-sapho-cno-study/