Background Undifferentiated arthritis (UA) is a form of peripheral arthritisthat does not fulfillthe classification criteria for a more definitive diagnosis. It was known that one third of patients with UA progressed into rheumatoid arthritis (RA). Studies showed that early use of disease-modifying anti-rheumatic drugs (DMARDs) in RA patients could delay the joint damage and therefore helped to improve the prognosis. So that early diagnosis and treatment might help with decisions with regard to early therapeutic intervention for a better prognosis. Antibodies to cyclic citrullinated peptide (anti-CCP) have been documented extensively over recent years as highly specific serological markers for RA diagnosis and prognosis.

In this article, we aimed to find out whether there were predictive factors in UA patients that would line out those patients at the greatest risk of developing RA so that early diagnosis and appropriate treatment could be performed to ameliorate their conditions.

Objectives Rheumatoid arthritis (RA) is an inflammatory disease of unknown cause. This article aimsto investigate the prognosis of undifferentiated arthiritis (UA) and to estimate the putative predictors contributing to early identification of RA from UA, thus improve appropriate medical intervention and a better prognosis.

Methods A retrospective cohort study of 218 patients with an initial diagnosis of UA and 2-year follow-up monitoring was carried out. Patients’ baseline information including Demographic variables, clinical features, and laboratory data was collected. Univariate and multivariate logistic regression models were used to examine the predictors.

Results The prevalence of anti-CCP antibodies and IgM-RF was 11.93% and 25.23% at the baseline, respectively. After 2 years of follow-up, 20.18% patients evolved into RA, 33.03% patients remained undifferentiated, 25.23% patients went into remission, and 21.56% developed into other connective tissue diseases. Univariate analysis showed that age, anti-CCP antibodies, tender and swollen joint count, duration of morning stiffness were significantly associated with the progression from UA to RA, while multiple regression analyses showed anti-CCP antibodies, tender joint count and duration of morning stiffness were independently associated with the development of RA. Using the best cut-off points based on the results of our analysis, anti-CCP antibodies had a specificity of 88.51%, a sensitivity of 45.45%, a positive predictive value ( PPV ) of 50.00% and a negative predictive value (NPV) of 86.52%, while for IgM-RF, the specificity was 86.78%, the sensitivity was 36.36%, the PPV was 41.03% and the NPV was 84.36%. The area under the curve (AUC) for anti-CCP antibodies (0.68) was higher than IgM-RF (0.60) and the AUC for the combination of these two antibodies was significantly higher than each antibody tested alone (P<0.001).

Conclusions Our findings suggest that only the titer of anti-CCP antibodies, tender joint count, duration of morning stiffness, instead of IgM-RF could predict the development of RA; such information might help with decisions with regard to early therapeutic intervention for a better prognosis. Although the anti-CCP antibodies alone were better than the IgM-RF in predicting RA, a combination of these two still improved the diagnostic performance.

Disclosure of Interest None Declared