Background Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint swelling, tenderness, and destruction of synovial joints, leading to severe disability. Early diagnosis is important because early initiation of disease modifying treatments can significantly improve long term outcomes of patients with RA.
Most specialists rely on a combination of clinical acumen and laboratory studies to make a diagnosis. The rheumatoid factor assay (RF) has been used for over 50 years as part of the American College of Rheumatology (ACR) classification criteria despite its shortcomings. Thus, the anti-citrullinated peptide (anti-CCP) was developed as a diagnostic test for RA, with initial studies showing high sensitivity and specificity among RA patients even in the presence of other rheumatic diseases or infectious diseases. To date, there have been no published studies on the sensitivity and specificity of anti-CCP in the Philippines.
Objectives To determine the sensitivity and specificity of anti-CCP compared with RF assay in the Philippines.
Methods This is a cross-sectional analytical study, which reviewed medical records of patients with both RF and anti-CCP from Jan 2012 to Dec 2013. Inclusion criteria included presence of clinical synovitis in at least one joint as seen by a rheumatologist. Subjects were then scored using the 2010 ACR/EULAR RA classification criteria, which served as the gold standard. A diagnosis of RA was made with a score of ≥6. Sensitivity and specificity for RF, anti-CCP, and combined RF and anti-CCP were calculated.
Results Out of 334 records retrieved, 208 subjects were included. The ACR/EULAR RA classification criteria showed 41 cases with RA. The mean age of the group was 47±14 years, majority being female at 83.3%. The sensitivity and specificity of anti-CCP were both higher than RF assay for the diagnosis of RA, which were 87.8% and 100% versus 68.3% and 98.8%, respectively. When both RF and anti-CCP tests were combined, the sensitivity and specificity were 60.98% and 100%, respectively, which showed that anti-CCP alone still fared better as a diagnostic test.
Conclusions Anti-CCP is useful for the diagnosis of RA due to its higher sensitivity and specificity compared with RF or even in combination with RF assay. Therefore in the Philippine setting, it can be used alone as both a screening and confirmatory serological marker, because under the 2010 ACR/EULAR classification criteria for RA, both tests (RF and anti-CCP) are scored equally.
Disclosure of Interest None declared