Erythrocyte sedimentation rate, C-reactive protein level, and serum amyloid A protein for patient selection and monitoring of anti-tumor necrosis factor treatment in ankylosing spondylitis

Objective. To study the usefulness of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and serum amyloid A (SAA) for response prediction and monitoring of anti-tumor necrosis factor (anti-TNF) treatment in ankylosing spondylitis (AS) patients. Methods. Patients were included consecutively before starting etanercept or infliximab treatment. ASsessment in Ankylosing Spondylitis (ASAS) response, defined as a 50% improvement or an absolute improvement of 2 points of the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI; 0-10 scale), was assessed at 3 months. Inflammatory markers and the BASDAI were collected at baseline and 1 and 3 months. Longitudinal data analysis was performed to compare associations between inflammatory markers and the BASDAI over time by calculating standardized betas. Predictive values of baseline levels of inflammatory markers for ASAS response were calculated. Results. In total, 155 patients were included, of whom, after 3 months of treatment, 70% in the etanercept cohort and 71% in the infliximab cohort responded. All markers, notably SAA, decreased significantly (P