Performance of the ASAS Health Index for the Evaluation of Spondyloarthritis in Daily Practice.

Objective: The Assessment of SpondyloArthritis international Society Health Index (ASAS HI) is a tool designed to assess disease impact in spondyloarthritis (SpA), but its clinical performance is barely known. We aimed to test the clinimetric properties of ASAS HI in a real clinical setting.
Methods: This cross-sectional study included 111 consecutive patients with SpA. The measurement properties of ASAS HI were tested against conventional assessment measures. Convergent validity was assessed by Spearman rho correlations, while discriminative validity was analyzed through receiver-operating characteristic (ROC) curves. A multivariate regression analysis was designed to identify ASAS HI items associated with active disease.
Results: The average ASAS HI was 5.4 ± 3.8 (interquartile range 3-8). ASAS HI showed high convergent validity against other SpA measures (rho ≥ 0.70, p < 0.0005). The optimal criteria for detecting high/very high disease activity Ankylosing Spondylitis Disease Activity Score (ASDAS) categories was an ASAS HI score > 6, area under the ROC curve 0.86 (95% CI 0.78-0.92), positive likelihood ratio 7.3 (95% CI 3.1-17.1), p < 0.0001. The ASAS HI items significantly associated with Bath Ankylosing Spondylitis Disease Activity Index active disease were "I often get frustrated" (OR 9.2, 95% CI 1.2-69.4, p = 0.032), and "I sleep badly at night" (OR 7.7, 95% CI 1.4-41.6, p = 0.018). As for ASDAS, it was "pain sometimes disrupts my normal activities" (OR 8.7, 95% CI 1.7-45.2, p = 0.010).
Conclusion: The ASAS HI is a useful and simple instrument for its application in daily practice. Given its good clinimetric properties, it could be used as an additional instrument to evaluate SpA.