ABSTRACT
Objective To investigate the clinical predictive value of rheumatoid factor (RF), anti-keratin antibodies (AKA), anti-cyclic citrullinated peptide (anti-CCP) antibody and anti-perinuclear factor (APF) in the transition from undifferentiated arthritis (UA) to rheumatoid arthritis (RA), and to analyze the clinical relevant factors. Methods 271 patients with UA who were followed up for a year were enrolled into the investigation. RF was measured by the rate scatting immunity method. APF and AKA were detected by immuniofluorescence method(IFA). Anti-CCP was measured by ELISA. Erythrocyte sedimentation rate (ESR) was analyzed by Wilcoxon method. The duration of morning stiffness, the numbers of swelling and tender joints, tender joints involved and DAS28 score were recorded and analyzed. Results 99% patients who had four-antibody-positive finally convetted from UA to RA. The conversation rate for those who had two or more than two antibody-positive was 83.0% and 65.9% respectively. The sensitivity and specificity of RF and anti-CCP antibody-positive in those who converted from UA to RA was 77.8% and 80.5% respectively. The percentage of polyarticular swelling in antibody-negative, one-antibody-positive, two-antibody-positive, three-antibody- positive and four-antibody-positive was 48%, 57%, 59%, 70% and 70% respectively. Meanwhile, the percentage of multi-small-joint involvement was 71%, 71%, 72%, 76% and 83% respectively. The proportion of elbow involvement in antibody-negative patients was 72%, which was the highest among all joint area involvement. The conversion differences of the group with more than 3 swelling joints or more than 3 small joints involvement ranked the first and second in frequency. Conclusion The combined detection of these autoantibodies could increase the specificity of early diagnosis of RA. The more positive antibodies present, the more likely the concersion form UA to RA. The sensitivity and specificity of RF and anti-CCP-positive is high, so the latter is expected to become one of the diagnostic criteria. The polyarticular swelling and multi-small-joint involvement are valuable in predicting the transformation from UA to RA.