Background Tumor necrosis factor (TNF) inhibitors provide effective therapeutic benefit in reducing clinical symptoms of ankylosing spondylitis (AS), especially in the amelioration of spinal inflammation. Metrological measures represent a clinically useful outcome for the evaluation of therapeutic response and are associated with changes in radiological index and health-related quality of life.
Objectives We sought to investigate the predictors for the improvement of metrological outcome after treatment with TNF inhibitors in patients with AS.
Methods A total of 106 AS patients who have been treated with one of three TNF inhibitors, including infliximab, etanercept, or adalimumab, for up to 33 months were included in this study. We analyzed 137 cases, of which 96 patients have used single agent, 19 patients two agents, and 1 patient three agents because of inefficacy or side effects of previous agents. Clinical efficacy measures such as Assessment in SpodyloArthritis international Society 20% improvement (ASAS20), ASAS40, ASAS5/6, Bath AS Disease Activity Index (BASDAI), C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were evaluated before treatment and at 3 month and every 6 month after treatment. Bath AS Metrology Index (BASMI) and chest expansion were evaluated as metrological outcome measures at the same time.
Results Treatment with three TNF inhibitors including adalimumab (62 patients), etanercept (60 patients), and infliximab (15 patients) revealed a similar clinical efficacy. The rates of ASAS20 were 87.3%, 90.3%, 91.6%, 90%, 82.6%, and 90.7% at 3, 9, 15, 21, 27, and 33 months after treatment. Treatment with TNF inhibitors was associated with significant improvement in metrological measures at 3 months and through 33 months. BASMI significantly correlated with components of ASAS response criteria including Bath AS Functional Index (BASFI), BASDAI-spinal inflammation, patient's global assessment, and pain. Patients who achieved the ASAS20 response at 3 months showed significant improvement in BASMI and chest expansion which were maintained until 27 months, whereas ASAS20 non-responders did not have metrological improvement (Fig. 1A). The differences of BASMI and chest expansion from baseline in ASAS20 responders were most prominent at 3 months and continued to improve until 9 months, which were then followed by sustained improvements at a similar level. The improvement in BASMI at 9 month was significantly associated with changes in BASDAI-spinal inflammation, BASFI, and pain (Fig. 1B). Linear regression analysis revealed that difference in BASFI from baseline at 9 month was a significant predictor of improvement in metrological measures.
Conclusions The ASAS20 response at 3 month after treatment with TNF inhibitors is a good predictor for metrological outcome and improvement of BASFI at 9 month predicts reversibility of BASMI in AS.
Disclosure of Interest None declared