Anti-carp antibodies$$$

Anti-CarP autoantibodies are regarded as new biomarkers for RA. They are partly also positive for rheumatoid factor and ACPA negative arthritis.

ACPAs or autoantibodies against citrullinated proteins/peptides occur in patients with rheumatoid arthritis (RA). They have a higher sensitivity in the diagnosis of rheumatoid arthritis than rheumatoid factor (RF). In the meantime, autoantibodies against citrullinated peptides have been included in the ACR criteria. Negative are APCAs are like the RF in psoriatic arthritis (Chimenti MS et al. 2015). For certain ACPAs (anti-CCP autoantibodies) a correlation between antibody titer and disease activity has been proven (Böhm BO). This results in a reliable, good parameter for disease progression and prognosis and a good basis for individual therapy decisions.

Anti-CarP autoantibodies are new biomarkers for RA. These are directed against the carbamylated protein (anti-CarP). In a larger French cohort study (n=720 patients) anti-CarP autoantibodies proved to be good predictors for the development of rheumatoid arthritis. In this study, anti-CarP antibodies were found in about 1/3 of the patients (32.6%) - including 23.6% of patients who were negative for both ACPA and RF. Anti-CarP antibodies are also positive for rheumatoid factor and ACPA negative psoriatic arthritis (Chimenti MS et al. 2015).

Anti-CarP antibodies were associated with higher disease activity. Anti-CarP positive early arthritis was associated with a higher risk of developing erosions within 96 months (55.6% of anti-CarP positive patients compared to 37.3% of anti-CarP negative patients).

Anti-CarP antibodies- similar to antibodies against cyclic citrullinated peptide (ACPA) have a predictive probability of about 30% for the clinical occurrence of rheumatoid arthritis within one year in patients with arthralgias.

For early-stage patients who do not yet meet the ACR diagnostic criteria for rheumatoid arthritis, the detection of antibodies against cyclic citrullinated peptide has already established itself as an early disease marker. The detection of anti-CarP antibodies is possible in 20% of ACPA-negative RA patients. It indicates a more severe course of the disease.

1. Böhm BO (2018) Autoantibody diagnostics. In: Neumeier B et al. (Eds) Clinical guide to laboratory diagnostics. Elsevier GmbH S. 412-413
2. Chimenti MS et al (2015) Auto-reactions, autoimmunity and psoriatic arthritis. Autoimmune Rev 14:1142-1146.https://www.ncbi.nlm.nih.gov/pubmed/26254734