This study aimed to investigate the association between b/tsDMARDs treatment and the prevalence of hand joint deformity in patients with RA.

This cross-sectional study included RA patients enrolled between 2019 to 2024. Hand joint deformity was defined as the presence of specific deformities in any of 28 hand joints, including the metacarpophalangeal (MCP) joints I-V, proximal interphalangeal (PIP) joints I-V, and distal interphalangeal (DIP) joints II-V. Based on medication history, patients were categorized into two exposure groups: 1) those treated with conventional medicine (conventional synthetic disease-modifying antirheumatic drugs [csDMARDs] and/or glucocorticoids [GCs]), and 2) those receiving conventional medicine (csDMARDs and/or GCs) add-on b/tsDMARDs (including tumor necrosis factor inhibitors [TNFi], interleukin-6 inhibitors [IL-6i], or Janus kinase inhibitors [JAKi]). The key exposure was b/tsDMARDs use, and the primary outcome was hand joint deformity. Multivariable logistic regression was used to assess the association between b/tsDMARDs use and hand joint deformity. An interaction analysis between b/tsDMARDs use and disease duration was performed.

A total of 1083 RA patients with a mean age of 52.6 ± 12.4 years and median disease duration of 5 (2,11) years were included. Hand joint deformity was present in 25.4% (275/1083) of RA patients. Overall, 15.4% (167/1083) of patients were treatment naïve at enrollment. Methotrexate was most commonly used csDMARDs (68.9%, 746/1083). In total, 67.2% (728/1083) of patients received conventional medicine, and 17.4% (188/1083) received conventional medicine add-on b/tsDMARDs, including 4.9% (53/1083) with add-on TNFi, 3.9% (42/1083) with add-on IL-6i, and 8.6% (93/1083) with add-on JAKi. After 1:1 propensity score matching for age, sex and disease duration (n=188 in each group), the prevalence of deformity was significantly lower in conventional medicine add-on b/tsDMARDs group than in the conventional medicine group (27.1% vs. 61.7%, P < 0.001). This association was consistent across most specific deformity types. Specifically, the conventional medicine add-on b/tsDMARDs group exhibited markedly reduced prevalence of boutonniere deformity (6.9% vs. 14.4%), swan neck deformity (6.9% vs. 16.0%), ulnar deviation of MCP joints (8.0% vs. 19.1%), PIP joints hyperflexion (3.7% vs. 17.6%) and DIP joints hyperextension (0% vs. 2.1%, all P < 0.05, Table 1). Multivariable logistic regression analysis showed that b/tsDMARDs use was an independent factor associated with a lower prevalence of hand joint deformity (OR = 0.211, 95%CI: 0.129-0.345, P < 0.001) after adjusting for confounding factors (including age, sex, disease duration, active smoking, rheumatoid factor [RF], anti-cyclic citrullinated peptide antibody [ACPA], morning stiffness, pain visual analog scale [VAS], erythrocyte sedimentation rate [ESR], C-reactive protein [CRP], clinical disease activity index [CDAI] and modified total Sharp score [mTSS]). We also analyzed the association of IL-6i, TNFi and JAKi with the prevalence of deformity. After adjusting for such confounding factors, all types of b/tsDMARDs were independently associated with a lower prevalence of deformity (TNFi: OR = 0.216, 95%CI: 0.096-0.487; IL-6i: OR = 0.338, 95%CI: 0.154-0.742; JAKi: OR = 0.162, 95%CI: 0.084-0.311; all P < 0.05, Table 2). Interaction analyses showed that the significant association of b/tsDMARDs with a low prevalence of hand joint deformity was significantly stronger with longer disease duration (OR = 0.929, 95%CI: 0.890-0.969, P = 0.001). Specifically, significant interaction effects were observed for IL-6i (OR = 0.915, 95%CI: 0.852-0.981) and JAKi (OR = 0.884, 95%CI: 0.828-0.943, both P < 0.05).

In this contemporary Chinese cohort, one-fourth of RA patients had hand joint deformity. The use of b/tsDMARDs was independently associated with a significantly lower prevalence of hand joint deformity in RA. This association increased with the prolongation of the disease duration.