Body weight, gender and response to TNF-α blockers in axial spondyloarthritis.

The objective of this study was to determine whether BMI and gender could lead to a different response rate to anti-TNF agents in patients affected by axial SpA. One hundred and seventy patients with active axial SpA (defined as a BASDAI ≥ 4) treated with an anti-TNF agent [adalimumab (ADA), etanercept (ETA), infliximab (IFX)] were retrospectively evaluated. Patients were divided according to the baseline BMI as normal weight (BMI < 25), overweight (BMI 25-30) and obese (BMI ≥ 30). After 12 months of treatment a 50% improvement of the initial BASDAI (BASDAI50) was the primary end point and BASDAI ≤ 1 was the secondary end point. After 12 months of anti-TNF treatment, 67.8% of men and 46.2% of women reached the BASDAI50 (P = 0.01). According to BMI categories, the rate of BASDAI50 achievement decreased from 72.8% in normal weight subjects to 54.5% in overweight and 30.4% in obese subjects (P < 0.001). In the logistic regression analysis, the best independent predictors of failure to obtain a BASDAI50 response at the 12th month of therapy in axial SpA patients were female gender [odds ratio (OR) 3.23 (95% CI 1.52, 7.14)] and a BMI ≥ 30 [OR 3.57 (95% CI 1.15, 11.11)]. Analysing outcomes based on IFX therapy (the larger subgroup), the BASDAI50 response rate fell from 79.0% in normal weight subjects to 56.7% in overweight and 16.7% in obese subjects (P < 0.001). No significant differences were observed with ADA and ETA. Data suggest that being female, overweight and mostly obese is associated with a lower rate of success in obtaining response status in axial SpA patients treated with anti-TNF drugs. Body weight could represent a modifiable factor to reach the best outcome in axial SpA patients treated with TNF blockers.