ANTI CYCLIC CITRULLINATED PEPTIDE ANTIBODIES (ANTI-CCP) IN RHEUMATIC AND AUTOIMMUNE LIVER DISEASES

Background: Anti-CCP are present in 50-80% rheumatoid arthritis (RA) sera, mainly rheumatoid factor (RF) positive. Although detected in other rheumatic diseases, both autoimmune and non-autoimmune, their high specificity (>95%) makes an useful diagnostic tool in patients with arthritis. No data are at present available about their frequency in erosive osteoarthritis of the hands (EOA), a degenerative disease characterized by bone erosions inflammatory features, in type 1 autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC), autoimmune liver disorders sometimes associated with RA and positive for RF.Objectives: To evaluate the prevalence of anti-CCP in the sera of our patients with AIH, PBC and EOA and, as controls, with RA and psoriatic arthritis (PA).Methods: One hundred and eighteen AIH, 50 PBC, 38 EOA, 80 RA and 23 PA sera from patients attending our liver and rheumatology clinics were tested for IgG anti-CCP by a commercially available ELISA kit (DIASTAT TM, AXIX-SHIELD, UK). AIH, PBC and RA were diagnosed according to internationally accepted criteria. The presence of coexisting RA in AIH and PBC patients was retrospectively assessed from their clinical records. The diagnosis of EOA was based on the radiologic demonstration of central erosions in at least 2 proximal or distal interphalangeal joints of the hands. According to the manufacturer's instructions, results were expressed in U/ml and sera were considered positive when exceeding 5 U/ml.Results: Results are reported in the table. On the whole, 9%, 6%, 5%, 56% and 9% of AIH, PBC, EOA, RA and PA sera were positive for anti-CCP, respectively. RA positive sera showed the highest autoantibody titres (>100U/ml in 47% positive cases), while PA, EOA displayed significantly lower titres. In the only high titre serum (100U/ml) was from a patient with coexisting RA. In AIH anti-CCP were of intermediate-high titre and only 2 of the 11 positive sera were from patients with underlying RA. Even eliminating these two sera, anti-CCP titres were not significantly lower than those from RA sera anti-CCP +ve U/ml median (range) U/ml median (range) all sera +ve sera AIH (118) 11 (9%) <2 (<2-100) 10 (8-100) PBC (50) 3 (6%) <2 (<2-100) 9 (9-100) EOA (38) 2 (5%) <2 (<2-9) 8-9 RA (80) 45 (56%) 10 (<2->100) 60 (7->100) PA (23) 2 (9%) <2 (<2-25) 9-25 ld]Conclusion: 1. We confirm the good sensitivity of anti-CCP for the diagnosis of RA, where they are usually found at high titres. 2. These antibodies can be detected in a low proportion of PA and EOA sera at low titre. 3. In PBC, when present at high titre, anti-CCP may suggest the coexistence of RA. 4. In AIH anti-CCP occur in about 10% patients, with titres comparable to those of RA, also in the absence of RA. Whether these antibodies are the same as those of RA needs to be further investigated.Citation: , volume , supplement , year 2004, page Session: Humoral aspects of autoimmune disease