Continuous Improvement of Physical Functioning in Ankylosing Spondylitis Patients by Tumor Necrosis Factor Inhibitors: Three-Year Followup and Predictors

Objective. To establish the 3-year outcome and course of physical functioning and spinal mobility impairments in patients routinely treated with tumor necrosis factor inhibitors (TNFi) and to find predictors of physical functioning and spinal mobility impairments. Methods. Ankylosing spondylitis (AS) patients eligible for TNFi were followed in a 3-year prospective observational study. Prediction models were developed with linear mixed modeling. Bath Ankylosing Spondylitis Functional Index (BASFI) and Bath Ankylosing Spondylitis Metrology Index (BASMI) were used as outcome measures for physical functioning and spinal mobility. Results. A total of 257 patients were included and treated with etanercept (n=174) or adalimumab (n=83). Physical functioning improved significantly during the first 6 months after the start of TNFi. The BASFI score decreased from mean +/- SD 5.4 +/- 2.4 to 3.3 +/- 2.6 at 6 months, and stabilized thereafter (BASFI third year score mean +/- SD 3.6 +/- 2.5). The BASMI showed no significant changes over time. Lower baseline BASFI and BASMI scores predicted a better level of physical functioning and spinal mobility after 3 years of TNFi therapy. Other predictors for a better 3-year outcome and course of physical functioning included absence of comorbidity, physical activity, younger age, and lower body mass index at baseline. Conclusion. Physical functioning in routinely TNFi-treated AS patients improved up to 6 months and stabilized thereafter. Therefore, it would be better to extend the period of evaluation of TNFi treatment to 6 months rather than the 3 months currently used. The risk factors of long-term physical functioning found in this study might help to identify patients at risk at an earlier stage and improve treatment strategy.