The aim of this study is to compare the three classification criteria for rheumatoid arthritis (RA) in a large cohort of early arthritis patients. Patients who had at least one clinically swollen joint with disease duration no more than 1 year and age more than 18 years were enrolled. The clinical and laboratory parameters were recorded. The patients were diagnosed by two experienced rheumatologists. Undiagnosed patients were followed up every 3 months until 1 year. The sensitivity, specificity, and predictive value were compared among the early RA (ERA) criteria, the 1987 ACR criteria, and the 2010 ACR/EULAR criteria in this inception cohort of early arthritis patients. A total of 417 patients with inflammatory arthritis were recruited. By the end of 1 year follow-up, there were 399 patients (95.7 %) with a definitive diagnosis and 18 (4.3 %) patients remained as undifferentiated arthritis. Among the patients with definitive diagnosis, 202 (50.6 %) patients were diagnosed with RA and 197 (49.4 %) with non-RA. The sensitivity of ERA criteria was equal to 2010 ACR/EULAR criteria (both were 72.3 %), but much higher than 1987 ACR criteria (72.3 vs. 39.1 %, P < 0.001); the specificity of ERA criteria was comparable to 2010 ACR/EULAR criteria (87.8 vs. 83.2 %) and slightly lower than 1987 ACR criteria (87.8 vs. 92.4 %, P < 0.001). Unlike the complicated scoring system of 2010 criteria, the ERA criteria were more feasible to use in practice with five criteria only. The ERA criteria have a high sensitivity and more clinically feasibility in daily practice for early RA diagnosis.
Keywords: Arthritis; Classification criteria; Early; Rheumatoid.