Anticyclic citrullinated peptide autoantibodies in systemic lupus erythematosus.

Systemic lupus erythematosus is an autoimmune disease with protean manifestation. Arthritis is one of the most common manifestations seen in SLE. Anti-CCP Ab is a recently described autoantibody that has been claimed as a most sensitive and specific marker for the diagnosis of RA. Study was performed to see whether anti-CCP2 Ab is positive in lupus arthritis or not. Anti-CCP Ab, ANA, ds DNA, and APLA were estimated by ELISA. Anti-CCP2 Ab was positive in 22 cases (37.93%) of SLE. Mean value of anti-CCP (18.08±16.95 U/ml) was statistically significant (P<0.001) when compared to control (5.07±U/ml). A total of 44 (75.86%) patients with SLE had arthritis. In 29 (50.00%) cases, arthritis resembled RA along with classical features of SLE, while 15 cases (25.86%) had nonspecific lupus arthritis. In 13 cases (44.82%) of RA type lupus arthritis, anti-CCP2 Ab was positive, while only three (20%) nonspecific lupus arthritis cases had elevated anti-CCP. In 14 (24.13) patients with SLE, there was no arthritis, but in this group also (6/14) 42.85% cases had elevated anti-CCP. A total of 11 (50%) patients with duration less than 1 year had more anti-CCP 2 positivity when compared to disease duration between 1 and 3 years (27.27%) and disease duration more than 3 years (22.72%), but specifically, it was not significant. Our study concludes that anti-CCP2 is not a specific antibody for RA, but it is present in autoimmune diseases.