Background Ankylosing spondylits (AS) is a chronic inflammatory spondyloarthritis characterized by prominent axial ankylosis, peripheral arthritis, and enthesopathy. The Bath Ankylosing Spondylitis Metrology Index (BASMI), a metrologic assessment of spinal mobility, is well correlated with the change of spinal inflammation and soft tissue involvement. The Ankylosing Spondylitis Disease Activity Score (ASDAS), which incorporates the CRP or ESR values in addition to patient-reported outcome (PRO) measurements, is a new composite index to assess disease activity in AS. However, ASDAS as a predictive factor for the metrologic improvement in AS patients treated with TNF-blockers is still largely unknown.
Objectives To investigate whether ASDAS is a valuable predictive factor for the metrologic outcome in AS patients treated with long-term treatment with TNF-blockers.
Methods A retrospective study was conducted in a total of 113 patients who were treated with TNF-blockers (126 cases; 100 patients with single agent and 13 patients with two). Clinical efficacy was assessed using Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), patient's global assessment (PtGA), physician's global assessment (PhGA), pain, ASAS response criteria (ASAS20, ASAS40, ASAS5/6), BASDAI50, acute phase reactants (ESR, CRP), ASDAS, and BAMI10 at baseline and month 3, and then every six months up to month 33.
Results Mean age was 34.3±9.9 years and 89.4% was male. Three TNF-α blockers including etanercept (57 cases), adalimumab (56 cases), and infliximab (13 cases) showed a similar clinical efficacy. BASMI10, which reflects the spinal mobility, showed a significant improvement at month 33 compared to baseline (3.3±2.4 vs. 4.3±2.4, p<0.001). Changes of ASDAS-CRP were most prominent from baseline to month 3 and still sustained to month 9 (mean score: 3.8, 1.8, 1.5, 1.5, 1.4, 1.4, 1.3 at months 0, 3, 9, 15, 21, 27, 33). Improvements of BASDAI50 and ASAS20/40 were maintained to month 33. Decrease of BASMI10 at month 33 from baseline was significantly correlated with changes of ASDAS-CRP (r=0.383, p<0.001), BASDAI (r=0.497, p<0.001), BASFI (r=0.447, p<0.001), PtGA (r=0.342, p=0.002), PhGA (r=0.342, p=0.002), and pain (r=0.604, p<0.001) at month 3 from baseline. Furthermore, BASDAI50 responsiveness at month 3 showed a statistically significant correlation with change of BASMI10 at month 33 (r=-0.199, p=0.039). Multiple linear regression analysis was performed to identify independent predictive factors associated with improvement of BASMI10 at month 33. Variables examined included changes of ASDAS-CRP, PtGA, PhGA, and pain and BASDAI50 responsiveness at month 3. Change of ASDAS-CRP at month 3 (ASDAS-CRP: B coefficient 0.503, 95% CI 0.228-0.770, p<0.001) was proved to be the independent predictive factor for the improvement of BASMI10 at month 33.
Conclusions Improvement of ASDAS at month 3 may be a valuable predictive factor for metrologic outcome of long-term treatment with TNF-blockers in AS.
van der Heijde D et al. ASDAS, a highly discriminatory ASAS-endorsed disease activity score in patients with ankylosing spondylitis. Ann Rheum Dis 2009;68:1811–1818.
Disclosure of Interest None declared