The Ankylosing Spondylitis Disease Activity Score is a highly discriminatory measure of disease activity and efficacy following tumour necrosis factor-α inhibitor therapies in ankylosing spondylitis and undifferentiated spondyloarthropathies in China

Methods. Two hundred and thirty patients were included in our study. They consisted of patients with active AS (n = 87) and uSpA (n = 30) participating in a double-blind placebo-controlled randomized clinical trial of etanercept and patients with active AS (n = 58) and uSpA (n = 55) treated with infliximab. The disease activity and treatment effects were assessed by ASDAS, BASDAI, patient global and the acute inflammation score of lumbar and SI joints by MRI. Discriminatory ability of all the measures was analysed by standardized mean difference and t-score. Results. In both the AS and uSpA groups, ASDAS correlated well with patient global score (AS group: r = 0.65-0.72; uSpA group: r = 0.52-0.62), ESR (AS group: r = 0.57-0.81; uSpA group: r = 0.63-0.85) and CRP (AS group: r = 0.51-0.70; uSpA group: r = 0.61-0.76) both at baseline and in changes from baseline to 6 weeks after TNF-alpha inhibitor treatment. The ASDAS scores outperformed BASDAI, patient global score, ESR, CRP and the acute inflammation score by MRI in differentiating patients with different levels of disease activity and patients with different levels of change in both AS and uSpA groups. There was little difference in performance between the two versions of the ASDAS. Conclusion. The new ASDAS is a highly effective measure in assessing disease activity and a great discriminatory measurement to assess the efficacy of TNF-alpha inhibitor in Chinese AS patients and uSpA patients.