Effect of HLA-B27 status and body mass index on the clinical response to infliximab in ankylosing spondylitis patients

Background: Tumor necrosis factor-alpha inhibitors (infliximab) have changed the therapeutic approach to ankylosing spondylitis (AS). Body mass index (BMI) and HLA-B27 status may affect the response to infliximab. Methods: One hundred and seventy AS patients with active disease were enrolled in the study. Age, sex, disease duration, HLA-B27 status, and other demographics were obtained. Patients were classified according to their BMI to three groups clinical response was monitored using Bath AS disease activity index, at the time of initiation of treatment and 6 months later. Clinical response was defined as BASDAI50. Results: At baseline, all the groups were comparable. The median BMI of the responders was 25.4 kg/m2 while for the nonresponders it was 27 kg/m2. The normal weight and overweight AS patients have achieved the BASDAI 50 response after 6 months of infliximab treatment (P < 0.001) while the obese AS patients fail to achieve this response by infliximab alone and they need another drug (nonsteroidal anti-inflammatory drugs). The response was higher in HLA-B27 positive patients (42.5%) compared to the HLA-B27 negative patients (29%), the difference, however, was statistically insignificant. Conclusion: Obese AS patients are less likely to achieve a response to infliximab than normal weight AS patients