Background/Purpose: The efficacy of anti-TNF in the management of Ankylosing Spondylitis (AS) has been demonstrated in numerous controlled clinical trials. The objective of this study is to assess in Canadian routine clinical practice the 4-year outcomes in patients with AS treated with infliximab (IFX) and the performance of  Ankylosing Spondylitis Disease Activity Score (ASDAS), a new disease activity measure in AS.  

Methods: BioTRAC is an ongoing, prospective registry of patients initiating treatment for RA, AS, or PsA with infliximab or golimumab as first biologics or after having been treated with a biologic for less than six months. People with AS treated with infliximab who were enrolled between 2005 and 2012 were included in this analysis. Descriptive statistics were produced for clinical outcome measures and patient reported outcomes at baseline and follow-up assessments over four years. Within-group changes were assessed for statistical significance with the paired-samples Student’s t-test. The correlation of ASDAS with BASDAI and BASFI was assessed with the Pearson correlation coefficient. The correlation of these measures with MDGA was assessed with the Spearman’s rho.

Results: A total of 230 AS patients who had at least one follow-up assessment were included in this analysis, with a mean (SD) age of 45.7 (11.5) years and mean (SD) disease duration since diagnosis of 10.0 (10.1) years. Among these, 167, 116, 74, and 38 had a 12-, 24-, 36-, and 48-month assessment, respectively. At the time of enrollment in the registry, mean (SD) patient parameters were: C-reactive protein (CRP) = 16.9 (20.2) mg/dL, erythrocyte sedimentation rate (ESR) = 25.8 (20.2) mm/hr, morning stiffness = 74.6 (40.2), health assessment questionnaire (HAQ-DI) = 1.20 (0.61), physician global assessment of disease activity (MDGA) = 6.6 (1.9), BASDAI = 6.4 (2.1), BASFI = 6.1 (2.5), and ASDAS = 3.8 (1.0). By 6 months of treatment significant improvements (P<0.01) were observed in all clinical and patient outcome parameters studied, which were sustained or further enhanced over 48 months of treatment. 

Similar significant changes were observed in ASDAS, BASDAI, and BASFI over time providing evidence of construct validity and sensitivity to change. A strong positive linear correlation between ASDAS and BASDAI (r=0.85; P<0.001) and BASFI (r=0.76; P<0.001) was observed. The correlation of MDGA was strong with ASDAS (rho=0.73; P<0.001) and BASDAI (rho=0.70; P<0.001) and moderate with BASFI (rho=0.64; P<0.001).    

By 12, 24, 36, and 48 months 66% / 72% / 77% / 75% achieved Clinically Important Improvement in ASDAS (Δ ≥ 1.1) and 37% / 49% / 47% / 50%, achieved ASDAS Major Improvement (Δ≥ 2.0), respectively. The proportion of patients with very high disease activity (ASDAS > 3.5) decreased from 62.4% at baseline to 6.9% at 48 months.

Conclusion: The results of this Canadian, longitudinal, real-world observational study demonstrate that treatment with infliximab over four years is effective in reducing symptom severity and improving outcomes in patients with AS. Furthermore, the data from this registry confirm the validity and sensitivity to change of the ASDAS score in a real-world AS cohort.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/validation-of-the-ankylosing-spondylitis-disease-activity-score-and-effectiveness-of-infliximab-in-the-treatment-of-ankylosing-spondylitis-over-4-years-the-canadian-experience/