Anti-carbamylated protein antibodies in rheumatoid arthritis patients and their association with rheumatoid factor.

Objectives: To evaluate levels of anti-carbamylated protein (anti-CarP) antibodies in rheumatoid arthritis (RA) patients and to determine their association with serological parameters and disease activity. Methods: A cross-sectional study involving 105 multiethnic RA patients (48 rheumatoid factor [RF]-positive and 57 RF-negative patients) was conducted at Hospital Universiti Sains Malaysia, Kelantan, Malaysia, from January 2015 to February 2016. Fifty healthy controls (HCs) were included. C-reactive protein (CRP), RF, anti-cyclic citrullinated peptide (anti-CCP) and anti-CarP antibodies were measured. A health assessment questionnaire (HAQ) was administered to the study participants and 28-joint Disease Activity Score (DAS28) were obtained. Results: The level of anti-CarP antibodies was significantly increased in the RA patients compared with HCs (p=0.042). The presence of anti-CarP antibodies was significantly associated with RF (p=0.019) and the HAQ (p=0.010). A significant association between the presence of anti-CarP antibodies and the DAS28 was not found (p=0.632). Conclusion: Our study provides further evidence that the level of anti-CarP antibodies is significantly elevated in RA patients.