Significance of anti-CCP antibodies in modification of 1987 ACR classification criteria in diagnosis of rheumatoid arthritis.

To examine the incorporation of anti-CCP antibodies into the American College of Rheumatology (ACR) classification criteria for rheumatoid arthritis (RA) and to evaluate the advantages of the revised anti-CCP criteria in diagnosing Chinese patients. Patients who suffered from arthritic problems during the recent 2 years were selected from the Department of Rheumatology and Immunology of Peking University People's Hospital. The patients were divided into RA group and non-RA group according to the clinical diagnosis by experienced rheumatologists. The ACR criteria were revised in three ways: (1) replacement of rheumatoid nodules and erosions as criteria with anti-CCP antibodies (RA-6 criteria); (2) replacement of rheumatoid nodules with anti-CCP antibodies as a criterion (RA-7 criteria); (3) addition of anti-CCP antibodies (RA-8 criteria). The diagnostic value of ACR criteria and anti-CCP revised criteria (RA-6, RA-7, and RA-8) were evaluated by comparing the sensitivity and specificity of all criteria, in all subjects and in subjects with arthritis symptoms within 2 years. There were 604 patients included in the study totally, among whom 312 patients were diagnosed as RA and 292 were diagnosed as other rheumatic diseases by rheumatologists. For all the RA patients, the sensitivity and specificity of anti-CCP antibodies were 76.2% and 96%, respectively. Its specificity was much higher than RF (85.2%). For the patients with a disease duration less than two years, the sensitivities were 82.0%, 91.0%, 87.0%, and 87.0%, while the specificities were 95.6%, 83.9%, 95.6%, and 95.6%, respectively, according to 1987 ACR criteria, RA-6, RA-7, and RA-8 criteria. Among all the RA patients, the corresponding sensitivities were 92.3%, 96.8%, 94.6%, and 94.6%, and the specificities were 92.8%, 83.6%, 92.8%, and 92.8%, respectively. The 1987 ACR criteria have high sensitivity and specificity in established RA, but are less sensitive in early RA. The RA-6 criteria improve the sensitivity by reducing its specificity. The RA-7 criteria with replacement of rheumatoid nodules by anti-CCP antibodies increase the sensitivity without losing specificity, which may serve as new classification criteria in routine clinical practice, especially in early RA patients.