Biologic disease-modifying anti-rheumatic drugs are equally effective in psoriatic arthritis patients with low and high joint counts

Objective: A lack of representation in pivotal trials currently limits guidance for the use of biologic DMARDs (bDMARDs) in PsA patients with a low number of actively inflamed joints. The aim of this study was to compare the effectiveness of a first bDMARD in PsA patients with a low vs high number of affected joints.

Methods: PsA patients with available 66/68 joint count assessments were divided into low joint count (LJC) patients when presenting with <3 tender or <3 swollen joints or high joint count (HJC) patients with ≥3 joints in both categories. We studied drug retention as a joint count independent effectiveness variable in LJC and HJC patients in univariate and multivariable adjusted Cox regression models.

Results: A total of 197 LJC patients differed not only in joint counts, but also had lower enthesitis scores, less often dactylitis, less disability and a better health-related quality of life at first bDMARD initiation than 190 HJC patients. However, LJC patients were less often on conventional synthetic DMARDs (csDMARDs). Despite these differences at baseline, bDMARD retention was not significantly different between LJC and HJC patients in both crude and adjusted analyses [hazard ratio (HR) 1.09 (95% CI 0.76, 1.58), P = 0.52]. Furthermore, bDMARD retention was significantly better [HR 0.63 (95% CI 0.47, 0.85), P < 0.002] when administered with csDMARD co-therapy.

Conclusions: bDMARDs were similarly effective in terms of drug retention in patients with low and high joint counts. In the setting of absent remission and a significant disease burden, bDMARDs should not be withheld from patients because they exhibit only a low joint count.