AB0332 An audit to examine whether there is a correlation between levels of anti-cyclic citrullinated peptide (CCP) antibody titres and joint findings on musculoskeletal ultrasound scan in rheumatoid arthritis

Background Anti-CCP antibodies (Abs) currently make an important part of the workup in patients with suspected rheumatoid arthritis (RA) and can be detected prior to the development of symptoms [1]. They have been incorporated in the new ACR/EULAR classification criteria [2]. In situations of diagnostic uncertainty, musculoskeletal ultrasound (US) might aid in making the diagnosis of RA in a clinical setting. We only request an anti-CCP antibody (Ab) titre and US to examine proximal interphalangeal, metacarpophalangeal and wrist joints when the diagnosis of an inflammatory arthritis is unclear. Objectives To find out whether there is a correlation between the level of anti-CCP Ab titre and US changes in hand and wrist joints of patients with suspected RA. Methods The results of serum anti-CCP Ab titres of 107 patients who had been seen in the rheumatology outpatient clinics in 2011 at the Gloucestershire Royal Hospitals NHS Foundation Trust were analysed retrospectively. Results of serum anti-CCP Ab titres were classified into negative (≤7 u/ml), positive (8-600 u/ml) and strongly positive (>600 u/ml, in accordance with the laboratory reference range). 28 out of these 106 patients also had a musculoskeletal US after hand and wrist joints for clinical diagnostic needs. Results 64 patients had negative (≤7 u/ml) anti-CCP Ab titres. In this group, 17 US scans were performed of which 6 came back positive (35.3%) for synovitis. Anti-CCP Ab titres were strongly positive (>600 u/ml) in 16 patients. 5 US scans were performed in this group and all showed synovitis (100%). In the 27 patients who had positive (8-600 u/ml) anti-CCP Ab titres, 6 US scans were performed and one showed synovitis (16.7%). Conclusions Patients with strongly positive Anti-CCP Abs (>600 u/ml) may not need further confirmation of synovitis through requesting musculoskeletal US scans. In cases of diagnostic uncertainty, scans may still be required to provide further evidence even in the presence of negative anti-CCP Abs. The group who had positive anti-CCP Ab titres and yet normal scans pose an interesting clinical question. Should this group be treated on disease modifying drugs on basis of symptoms and CCP positivity even when there has been no detectable synovitis clinically or demonstrated on US scans? References van Gaalen, F.A., et al., Association between HLA class II genes and autoantibodies to cyclic citrullinated peptides (CCPs) influences the severity of rheumatoid arthritis. Arthritis and Rheumatism, 2004. 50(7): p. 2113-2121. Aletaha, D., et al., 2010 Rheumatoid arthritis classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative. Annals of the Rheumatic Diseases, 2010. 69(9): p. 1580-1588. Disclosure of Interest None Declared