Background/Purpose: Rheumatoid arthritis (RA), psoriatic arthritis (PsA), and axial spondyloarthritis (axSpA) share many clinical features but are differentiated by key clinical and molecular characteristics. Patients with RA are often seropositive (S+) for rheumatoid factor (RF) or anti-cyclic citrullinated peptide (CCP) antibodies, whereas those with PsA or axSpA are usually seronegative (S−) for these antibodies. Limited data are available comparing patients with S+ and S− RA, and few studies have compared disease burden across patients with S+ RA, S− RA, PsA, and axSpA. We compared clinical and disease characteristics among these 4 groups in the Corrona RA and PsA/SpA Registries.

Methods: Adult patients with RA enrolled in the Corrona RA Registry and those with PsA or axSpA enrolled in the Corrona PsA/SpA Registry between March 2013 and February 2019 were included. Patients with RA must have had nonmissing RF and anti-CCP values at enrollment and were classified as S+ (RF or anti-CCP ≥ 20 U/mL) or S− (RF and anti-CCP < 20 U/mL). Patient demographics, clinical characteristics, and disease activity and patient-reported outcome (PRO) measures collected at registry enrollment were compared between patients with S+ RA vs S− RA, PsA, or axSpA using t or Wilcoxon rank-sum tests for continuous variables and χ² or Fisher exact tests for categorical variables.

Results: A total of 4827 patients with S+ RA, 1959 with S− RA, 3001 with PsA, and 512 with axSpA were included. Patients with S− RA had a higher prevalence of comorbidities than those with S+ RA, including fibromyalgia (13.1% vs 5.9%) and depression (22.7% vs 17.6%) (Table 1). Patients with axSpA had a lower prevalence of comorbidities than those with S+ RA; there was no clear trend in prevalence of comorbidities between patients with PsA and S+ RA. Overall biologic and prednisone use were comparable between patients with S+ and S− RA, whereas patients with PsA or axSpA had more biologic use and less prednisone use than those with S+ RA (Table 2). Prior csDMARD use was higher among patients with S− RA and lower among patients with axSpA than those with S+ RA; current csDMARD use was comparable between patients with S+ and S− RA but lower among those with PsA or axSpA. Patients with S+ RA had higher swollen joint counts, ESR, and CRP levels than those with S− RA, PsA, or axSpA, and higher tender joint counts than those with PsA and axSpA (Table 3). Patients with S+ RA had a higher mean physician global assessment score than those with S− RA or PsA but lower than those with axSpA. Patients with S+ RA had a mean patient global assessment score comparable with that of patients with S− RA but lower than those with PsA or axSpA.

Conclusion: Patients with S− RA had a higher comorbidity burden but similar treatment profiles and PRO scores compared with those with S+ RA. Patients with PsA or axSpA had more biologic use and worse PRO scores than those with S+ RA. These results demonstrate the differences in disease manifestations of patients with these diseases. Further studies are needed to identify factors that differentiate these disease groups, particularly regarding therapeutic response.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/characteristics-of-patients-with-seropositive-or-seronegative-rheumatoid-arthritis-psoriatic-arthritis-or-axial-spondyloarthritis-data-from-the-us-based-corrona-rheumatoid-arthritis-and-psoriatic-a/