Anti-carbamylated protein antibodies presence in early arthritis with a poorer clinical and radiological outcome: data from the French ESPOIR cohort

Objectives To assess the prevalence of anti-carbamylated protein (CarP) antibodies in a French cohort of early arthritis and to investigate their association with clinical features, final diagnosis, prognosis and comorbidities. Methods The presence of anti-CarP antibodies among patients with early arthritis belonging to the ESPOIR French cohort (n=720) was determined using ELISA. We calculated the prevalence of anti-CarP antibodies in different patient subgroups that were stratified according to their anti-citrullinated peptides antibodies (ACPA) and/or rheumatoid factor (RF) status. Diagnosis and prognosis values of the test were evaluated in this population. Results We observed the presence of anti-CarP in approximately one third of the patients (32.6%) and 23.6% of the RF and/or ACPA sero-negative patients. Anti-CarP positivity was associated with a more active disease status at baseline and over time with a significantly higher DAS28-ESR level at M36 (3.1±0.11 vs. 2.8±0.06, p=0.03). Anti-CarP-positive early arthritis was associated with a higher risk of developing erosions after 96 months of follow-up (55.6% among the anti-CarP+ patients vs. 37.3% among the anti-CarP- patients, OR=2.1 [1.2-3.6], p=0.009). This association was particularly true when anti-CarP was associated with ACPA positivity. Moreover, ACPA positivity alone-early arthritis was not associated with a higher risk of erosive evolution. Conclusions Anti-CarP antibodies were present among one third of patients with early arthritis and among one fourth of the RF-negative and ACPA-negative patients. They were particularly associated with a more severe radiographic fate. Anti-CarP antibody positivity may help to accurately identify those at-risk of erosive evolution in an early arthritis population. This article is protected by copyright. All rights reserved.