Background/Purpose: Autoantibodies (RF or ACPA) are found in sera from patients with palindromic rheumatism (PR) but there are no studies analyzing the presence of Anti-carbamylated proteins antibodies (Anti-CarP) in patients with PR. The aim of this study was to analyse the prevalence of Anti-CarP in patients with PR and to evaluate their clinical significance and association with autoantibody status (RF and ACPA).

Methods: Patients with pure PR (not associated with any rheumatic disease at the time of serum measurement) with sera collected between June 2012 and June 2013 were included (Cabrera-Villalba S et al J Rheumatol 2014;41:1650-5). Anti-CarP were determined by a home-made ELISA test using a synthetic chimeric fibrin/filaggrin homocitrullinated peptide (CFFHP) as antigen. IgG, IgA and IgM isotype were measured using the corresponding secondary antibodies. Cut-off values were determined using ROC curves, with a specificity of 98% compared with a healthy population. ACPA, RF, progression toward persistent arthritis fulfilling ACR/EULAR RA criteria, and remission (no joint attacks in the last 6 months) was analyzed during the follow-up (until May 2017). Patients were treated according to physician criteria. A control group of established RA patients was also included.

Results: Anti-CarP antibodies were analyzed in 54 patients with pure PR and 53 patients with established RA controlled by age, gender and disease evolution. ACPA (CCP2) was positive in 64.8% of PR and 66.0% of RA patients. Anti-CarP were found in 9 out of 54 (16.7%) of PR patients. Patients with PR and Anti-CarP (+) were all ACPA positive and presented higher ACPA titers than Anti-CarP (-) patients (Table 1). In PR patients, IgG was the predominant isotype (100%) and only one patient presented IgA (11.1%) and none IgM. In the RA control group, the prevalence of Anti-CarP was 39.6% and the percentages of IgG, IgA and IgM were 57.1%, 47.6% and 38.1% of Anti-CarP (+) patients respectively. DMARDs were administered in 64.8% of patients (in all Anti-CarP (+) patients) at the last assessment, mainly antimalarials and methotrexate. More Anti-CarP (+) patients developed RA (33.3% vs. 16.3%) during follow up although the difference was not significant. Remission was more frequent in Anti-CarP negative patients (Table 1).

Conclusion:

Table 1. Clinical and serological characteristics of PR patients according to Anti-CarP status

* At the time of serum measurement

**: From sera measurement to last follow-up

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/anti-carbamylated-protein-antibodies-carp-in-palindromic-rheumatism-prevalence-and-clinical-significance/