ASAS Health Index in patients with spondyloarthritis and its association with disease activity and disease burden including fibromyalgia.

Objectives: To evaluate the association of the Assessment of Spondyloarthritis international Society Health Index (ASAS-HI) with disease activity and disease burden in patients with spondyloarthritis (SpA).

Methods: Observational, cross-sectional and single-centre study from the Córdoba AxSpA Task force, Registry and Outcomes (CASTRO). Scores related to disease activity (BASDAI and ASDAS), functionality (BASFI), structural damage, mobility, health and the presence of concomitant fibromyalgia (FM) were obtained from all patients. ASAS-HI score was considered the main outcome. Pearson's r statistic, Student's t test, and univariate and multivariate linear regressions were performed to assess the association between the ASAS-HI score and the studied covariates.

Results: A total of 126 SpA patients were included. The mean ASAS-HI score was 4.6±3.9, showing a "strong" positive linear correlation (r>0.60) with the BASDAI and BASFI and a "moderate" positive linear correlation (r=0.40 to 0.60) with the global VAS and ASDAS. Patients with FM showed a significantly higher ASAS-HI score than patients without FM (9.5±3.2 vs. 3.7±3.4, respectively, p<0.01). Multiple linear regression showed that 57.4% of the ASAS-HI variability (R2=0.574) was explained by the presence of concomitant FM (β=2.23, 95% CI 0.73 to 3.80, p=0.004), higher scores on the BASDAI (β=0.62, 95% CI 0.25 to 0.97, p=0.001) and BASFI (β=0.57, 95% CI 0.26 to 0.88, p=0.001).

Conclusions: The impairment of health in patients with SpA was mainly associated with high disease activity, worsening functionality and with the presence of a possible concomitant FM. Therefore, in patients with high ASAS-HI scores we must evaluate the presence of concomitant FM.