ASAS Health Index Valid, Reliable in Axial and Peripheral Spondyloarthritis

The Assessment of Spondyloarthritis International Society Health Index (ASAS HI) has proven to be a valid, interpretable, reliable, and responsive questionnaire that can be used to evaluate the effect of spondyloarthritis (SpA) and its treatment on functioning and health, which may help facilitate a comparison of the effect of disease among various patient populations. Results of the observational study were reported in the Annals of the Rheumatic Diseases.

The investigators sought to assess the construct validity, interpretability, reliability, and responsiveness of the ASAS HI, along with a determination of cutoff points for good and poor health, within the original English version and 18 translations in 23 countries around the world in patients with SpA.

A total of 1548 patients who fulfilled the ASAS classification criteria for axial spondyloarthritis (axSpA) or peripheral SpA were enrolled in the study. Overall, 64.9% were men and the mean age was 42.0±13.4 years. In the analysis, construct validity ranged from low to high; ASAS HI showed a weak correlation with age (r=0.10) and a high correlation with the Bath Ankylosing Spondylitis Functioning Index (r=0.71). The internal consistency was high per Cronbach’s α (0.93). The reliability was good among 578 participants (intraclass correlation coefficient, 0.87; 95% CI, 0.84-0.89). The responsiveness among 246 patients was moderate to large; the standardized response mean was −0.44 for nonsteroidal anti-inflammatory drugs, −0.69 for conventional synthetic disease-modifying antirheumatic drugs, and −0.85 for tumor necrosis factor inhibitors.

The smallest detectable change was calculated as 3.0, which corresponds to the minimum change beyond measurement error that can be identified in an individual patient over time. Values of ≤5.0 have balanced specificity for distinguishing good health, in contrast to moderate health, and values ≥12.0 represent poor health as opposed to moderate health.

The investigators concluded that in this global study of patients with axSpA or peripheral SpA, the ASAS HI is a valid, reliable, responsive tool that can be used to assess the effect of the disease and its treatment on patients’ overall functioning and health.

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Reference

Kiltz U, van der Heijde D, Boonen A, A et al. Measurement properties of the ASAS Health Index: results of a global study in patients with axial and peripheral spondyloarthritis [published online June 1, 2018]. Ann Rheum Dis. doi: 10.1136/annrheumdis-2017-212076