A Comparative Assessment of the Diagnostic Value of Anti-cyclic Citrullinated Peptide Antibodies and Rheumatoid Factor in Rheumatoid Arthritis

Rheumatoid arthritis is a systemic, chronic inflammatory autoimmune disease affecting many tissues but principally attacking the joints. Auto antibodies such as rheumatoid factor and anti-cyclic Citrullinated peptide antibodies have important diagnostic value. This cross-sectional analytical study was performed at a single medical institution in central Iran (Shahid Sadoughi Hospital, Yazd, Iran) in order to compare the diagnostic value of anti-cyclic citrullinated peptide antibodies and rheumatoid factor in patients with rheumatoid arthritis. Serum levels of anti-cyclic citrullinated peptide antibodies were determined by enzyme-linked immunosorbent assay, and levels of rheumatoid factor were determined by turbidimetry on a latex-enhanced agglutination assay in 266 patients with rheumatoid arthritis and 134 patients with non-rheumatoid arthritis rheumatic diseases. Among the 266 patients with rheumatoid arthritis, 188 patients (70.7%) were tested positive for anti-cyclic citrullinated peptide antibodies, and 123 patients (46.2%) were tested positive for rheumatoid factor. The sensitivity, specificity, positive predictive value and negative predictive value of anti-cyclic citrullinated peptide antibodies for diagnosing rheumatoid arthritis were 70.76%, 85.07%, 90%, and 59% respectively. Those for rheumatoid factor were 46.26%, 90.29%, 90%, and 45% respectively. The anti-cyclic Citrullinated peptide antibodies measurement is a useful test for diagnosing rheumatoid arthritis. Due to its high positive predictive value and negative predictive value, it is an important diagnostic test and gives accurate diagnosis of the disease. However, this does not mean that anti-cyclic citrullinated peptide antibodies can replace rheumatoid factor in the diagnosis of rheumatoid arthritis, because not all rheumatoid arthritis patients have anti-cyclic Citrullinated peptide antibodies. The two tests therefore appear to be complementary.