Site-specific articular response to TNF inhibitor in axial spondyloarthritis: A European cohort study

In patients with psoriatic arthritis, articular responses vary by joint location with both tumour necrosis factor inhibitors (TNFi). It remains unknown whether this also applies to patients with axial spondyloarthritis (axSpA).

We included patients with axSpA from the European spondyloarthritis research collaboration network (EuroSpA RCN) who initiated a TNFi between 2001-2022. Joint tenderness was used as a proxy for peripheral articular involvement. Among patients with at least one tender joint at treatment start (baseline) based on a 26-joint count (28-joint count excluding the shoulders), resolution of joint tenderness during a two-year follow-up was assessed with a mixed-effects model for interval-censored data, including random effects for country and patient.

A total of 1113 patients (43.4% male, mean (SD) age 44.7 (11.7) years) with 5886 tender joints (median (IQR) 3 (2,7) tender joint count) from eight European countries initiating treatment with a TNFi (n=1113) were included. The knee and wrist were most commonly affected at baseline. Compared with the wrist, the rate of joint tenderness resolution was similar in the elbow (HR=1.06, 95%CI 0.88 to 1.28), lower in the knee (HR=0.76, 95%CI 0.64 to 0.90), while higher in all finger joints, particularly in the first interphalangeal joint (HR=2.64, 95%CI 2.05 to 3.40) and in digits four and five (metacarpophalangeal joint (MCP)4 HR=2.19, 95%CI 1.77 to 2.71) and MCP5 (HR=3.16, 95%CI 2.50 to 4.00).

The peripheral joint response to TNFi in axSpA appears to be location-dependent, indicating that the joint site should be considered when interpreting treatment response.