Is It Necessary to Combine Detection of Anticitrullinated Protein Antibodies in the Diagnosis of Rheumatoid Arthritis?

Objective.Antibodies against citrulline-containing epitopes, such as antiperinuclear factor (APF), antikeratin antibodies (AKA), antifilaggrin antibodies, and anticyclic citrullinated peptide (anti-CCP) antibodies, are specific in rheumatoid arthritis (RA). Detection of APF, AKA, and anti-CCP has been widely used in clinical practice. However, studies on combined detection of these anti citrullinated protein antibodies (ACPA) in the significance of diagnosing RA have been limited. We aimed to detect APF, AKA, and anti-CCP antibodies and to evaluate the significance of combined detection of these ACPA in RA.Methods.A total of 551 patients with arthritic disorders, 304 with RA and 247 with other rheumatic diseases, were selected at the Department of Rheumatology and Immunology during the past 2 years. AKA and APF were tested by indirect immunofluorescence assay. Anti-CCP was detected using the second-generation ELISA kit.Results.The sensitivities of anti-CCP, AKA, and APF tests for RA were 76.2%, 43.4%, and 34.5%, respectively, while the specificities were 96.0%, 98.4%, and 99.6%. The combination of anti-CCP, AKA, and APF positivity had the highest specificity (100%), but it yielded a low sensitivity (28.3%). When 2 of the 3 ACPA were positive, the sensitivity and specificity were 48.4% and 99.2%, respectively. When either anti-CCP or AKA or APF was positive, sensitivity increased to 77.3%, but specificity decreased to 94.7%.Conclusion.Anti-CCP was the most valuable marker in the diagnosis of RA, among the 3 ACPA. Combined detection of anti-CCP, AKA, and APF did not increase the diagnostic capability for RA.