The European Portuguese version of the ASAS Health Index for Patients with Spondyloarthritis: Measurement properties

OBJECTIVE: The Assessments of SpondyloArthritis international Society Health Index (ASAS HI), estimates the impact of Spondyloarthritis (SpA) on global functioning and health. This article assesses the construct validity, reliability and responsiveness of the Portuguese version of the ASAS HI. PATIENTS AND METHODS: Patients fulfilling ASAS classification criteria for axial (axSpA) or peripheral SpA (pSpA) were included. Construct validity was assessed through Spearman’s correlation analysis with other health outcomes. Discriminant validity was tested comparing the ASAS HI across disease activity and functional states using the Kruskal–Wallis test. Internal consistency was assessed by Cronbach’s α, and test-retest reliability by intraclass correlation coefficients (ICC). Responsiveness was evaluated by the standardized response mean (SRM) in patients with active disease who required therapy escalation. RESULTS: Among the 91 patients included, 67% were male, mean (SD) age 47.2 (12.9) years, 63 patients with axSpA and 28 patients with pSpA. The hypothesis defined a priori to test construct validity were confirmed. The ASAS HI showed ability to discriminate between patients with different disease activity and functional states (p<0.001). Internal consistency (Cronbach’s α: 0.88) and test-retest reliability [ICC=0.76 (95%CI 0.09-0.91)] were good. Responsiveness was moderate (SRM=-0.53). The smallest detectable change was 3.0. CONCLUSIONS: The Portuguese version of the ASAS HI is a comprehensible questionnaire that is valid, reliable and responsive. It can be used to assess the impact of SpA and its treatment on functioning and health, in clinical practice and for research purposes.