Objective: To determine the prognosis of undifferentiated polyarthritis syndrome in the clinic compared with rheumatoid arthritis (RA).
Methods: We identified consecutive patients seen within the first 2 years of disease (and further subset into 6-month groups) diagnosed as having either RA or undifferentiated polyarthritis syndrome at the first clinic visit. Undifferentiated polyarthritis syndrome was characterized by clinical presentation, laboratory data, and American College of Rheumatology (ACR) 1958 and 1987 RA criteria. Followup evaluations were done to determine change in diagnosis, resolution of symptoms, and clinical remission of RA.
Results: Undifferentiated polyarthritis syndrome was more common in the clinic than RA (638 vs 503). Of patients with RA 7.6% were symptom free an average of 6.9 years after the first clinic visit. For those with disease onset between 0-6 months and 0-2 years, complete resolution of undifferentiated polyarthritis syndrome occurred in 57.9 and 53.9% of cases, including 46.1 and 35.6% meeting ACR 1987 criteria for RA. Latex positivity was the strongest predictor of failure to resolve subsequently (25.0 and 29.2% resolution) and the best predictor of development of RA (41.7 and 43.1%).
Conclusions: Nonrheumatoid undifferentiated polyarthritis syndrome is more common in the clinic than RA. Undifferentiated polyarthritis syndrome resolves in more than half the cases, while RA remits in 7.6%. Finally, resolution of RA criteria positive undifferentiated polyarthritis syndrome occurs predominantly in those who are seronegative.