Fat mass reduces response to TNF-α blockers in patients with ankylosing spondylitis
Higher body fat content at baseline in patients with ankylosing spondylitis (AS) is likely to weaken response to treatment with tumour necrosis factor-α (TNF-α) blockers, measured by the Ankylosing Spondylitis Disease Activity Score containing C-reactive protein (ASDAS-CRP) and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), suggests a recent study.
This may also lead to lower response rates in female patients. In addition, a trend toward muscle mass recovery is seen in male patients after treatment.
Researchers investigated the relationship between body composition and response to TNF-α blocker treatment in AS patients, and examined the change in body composition after treatment, accounting for sex and age. All participants met the modified New York criteria for AS and were naïve to TNF-α blocker.
Patients were followed for a minimum of 6 months following the initiation of etanercept or adalimumab. ASDAS-CRP and BASDAI were reported. The investigators used whole body dual-energy X-ray absorptiometry to assess body composition. Body fat percentage (BF%), fat mass index (FMI), and fat free mass index (FFMI) were reported as absolute values and as percentiles.
A total of 41 patients (61 percent men) were included, with a median follow-up of 14.3 months (interquartile range, 8.4 to 19.4).
Multivariate regression analysis revealed that more fat at baseline (whether BF%, FMI or FMI percentile) significantly correlated with a lower change of achieving a clinically important improvement in the ASDAS-CRP or BASDAI after treatment.
No significant change was observed in the body composition after treatment. However, there was a trend toward muscle recovery in men (FFMI change from 34.0th to 37.4th percentile), according to researchers.