Comorbidity and response to TNF inhibitors in axial spondyloarthritis: longitudinal analysis of the BSRBR-AS.

ABSTRACT

OBJECTIVE: Comorbidities influence disease assessment in axial spondyloarthritis (axSpA), but their association with response to TNF inhibitors (TNFi) is unclear. We examined associations between comorbidity history at TNFi initiation and (i) change in disease indices over time; (ii) binary response definitions; and (iii) time to treatment discontinuation. METHODS: We studied participants starting their first TNFi from a national axSpA register. Comorbidity categories were created from 14 physician-diagnosed conditions and compared against change in disease indices over time using linear mixed effects models; BASDAI50/2 (50% or 2-unit reduction) and BASDAI < 4 at 6 months using logistic models; and time to treatment discontinuation using Cox models. Models were adjusted for age, gender, BMI, deprivation and education. RESULTS: In total, 994 were eligible for analysis (68% male, mean age 45 years); 21% had one comorbidity and 11% had ≥2. Baseline disease severity was higher in those with comorbidities across all indices, but absolute improvement over time was comparable for BASDAI and spinal pain. Participants with ≥2 comorbidities had smaller absolute improvement in BASFI and quality of life. This group also had numerically reduced odds of achieving BASDAI50/2 [odds ratio (OR) 0.81; 95% CI 0.45, 1.45] and BASDAI < 4 (OR 0.57; 95% CI 0.32, 1.04). Treatment discontinuation was increased in those with two comorbidities [hazard ratio (HR) 1.32; 95% CI 0.88, 2.00] and ≥3 comorbidities (HR 2.18; 95% CI 1.20, 3.93) compared with none. CONCLUSIONS: Participants with multiple comorbidities had poorer treatment outcomes, particularly increased treatment discontinuation and poorer improvements in function and quality of life. These results inform clinicians and educate patients about response to the first TNFi given comorbidity burden.