Incidence of septic arthritis in patients with ankylosing spondylitis and seropositive rheumatoid arthritis following TNF inhibitor therapy.

OBJECTIVES: Septic arthritis (SA) is a serious complication occurring in the joints, and its risk increases with immunosuppressive therapy. This study investigated whether TNF inhibitors increase the risk of SA in patients with AS and seropositive RA (SPRA). METHODS: We searched the South Korean Health Insurance Review and Assessment Service database for incident cases of AS and SPRA between 2010 and 2020. SA was defined using the diagnostic code M00 and hospital admission. Cox-proportional hazards analysis was conducted to compare the incidence of SA according to TNF inhibitor (infliximab, etanercept, adalimumab/golimumab) use during follow-up. RESULTS: Of the 145 129 patients analysed, 1170 (0.8%) developed SA during the follow-up period. Older age; male sex; SPRA diagnosis; comorbidities of hypertension (HTN), diabetes mellitus (DM) and chronic pulmonary disease (CPD); and infliximab and etanercept use increased the incidence of SA in the overall population. However, in patients with AS, only age and renal disease were predictors of SA, and TNF inhibitors did not increase the incidence of SA. Meanwhile, patients with SPRA treated with TNF inhibitors were prone to SA regardless of TNF inhibitor type, and age, HTN, DM and CPD were associated with SA. The incidence of SA was prominent after the first year of commencing TNF inhibitor therapy, for both AS and SPRA. CONCLUSION: TNF inhibitors increase the incidence of SA, specifically in patients with SPRA, but not AS. Importantly, age, comorbidities and the early time period after starting TNF inhibitors were associated with SA, which should be considered simultaneously when initiating TNF inhibitor therapy.

Differing X-ray patterns in seronegative and seropositive rheumatoid arthritis.

INTRODUCTION: Anti-citrullinated protein antibody (ACPA) and rheumatoid factor (RF) status are important predictors for rheumatoid arthritis (RA) erosivity. Qualitative differences on hand/feet radiographs have been described, indicating more carpal fusion in seronegative RA. This study explores these differences further using the total Sharp/van der Heijde score (TSS), digital X-ray radiogrammetry (DXR), and qualitative description. METHODS AND MATERIALS: Matched seronegative (ACPA negative, RF negative, snRA) and seropositive (ACPA, RF > 3xULN, spRA) were examined. TSS scores both for erosions and joint space narrowing (JSN) were registered separately and compared for both groups. Joint compartments and single joints were compared, using a heat map. The degree of carpal fusion was quantified 0-5. DXR measurements (bone mineral density, cortical thickness, bone width, metacarpal index) were determined for each hand separately. Finally, selected radiographs were examined unblinded to search for non-quantifiable differences. RESULTS: A total of 56 snRA and 57 spRA patients were examined. spRA patients had more erosions and joint space narrowing. Erosion load differed significantly between spRA and snRA in the foot and metacarpophalangeal joint, but not in the wrist or proximal interphalangeal joint compartments. Intracompartmental differences were greater in spRA. JSN scores were greater in spRA, in all compartments except wrist. Carpal fusion and DXR scores did not differ between the groups. The qualitative comparison showed that snRA patients displayed periarticular ossifications, carpal shortening, and sparing of the CMC joints, whereas spRA patients had more CMC damage and less shortening. CONCLUSION: X-ray manifestations in snRA and spRA are qualitatively and quantitatively different. This suggests pathophysiological differences between the two forms. Key Points • Seronegative and seropositive RA display qualitatively and quantitatively different X-ray patterns, suggesting differences in the underlying pathophysiological process. This is the first time that this has been shown in a systematic, quantitative fashion.