Objectives. Our PRIMARY objectives are to evaluate the sensitivity, specificity, and positive likelihood ratios (+LR) of anti-Sa Abs to identify among patients with early polyarthritis (EPA) in the first 12 months of disease (median 4 months) those that will, at 18, 30, 42 and 60 months into disease : 1- have persistent arthritis; 2- satisfy American College of Rheumatology (ACR) criteria for RA; 3- have developed a SEVERE disease (as defined by their Sharp/van der Heijde radiological score or their modified Health Assessment Questionnaire (M-HAQ) score, as well as by our composite index that includes both scores).