Objective: To validate a model which predicts progression from undifferentiated arthritis (UA) to RA, in a Canadian UA cohort.
Methods: The prediction rule, comprising variables which are scored from 0 to 13, with higher scores reflecting an increased risk of RA, was applied to baseline characteristics of all patients with UA. Progression to RA was determined at 6 months.
Results: 105 patients were identified. By 6 months, 80 (76%) had developed RA while 25 (24%) had developed another diagnosis. Number of tender and swollen joints, rheumatoid factor positivity, anti-cyclic citrullinated peptide positivity, poor functional status and high disease activity were associated with development of RA (p<0.01). Median prediction score was 8.0 for progressors, 5.0 for non-progressors. With these cut-off points, 18 (72%) patients with scores ⩽5 did not develop RA, while 35 (97%) with scores ⩾8 did develop RA.
Conclusions: High scores in our cohort predicted those who progressed to RA by 6 months. Baseline scores ⩾8 corresponded with higher rates of progression.
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▸ An additional appendix is published online only athttp://ard.bmj.com/content/vol68/issue9
Funding The study was sponsored by an unrestricted research grant provided by Amgen Canada Inc and Wyeth Pharmaceuticals. The sponsors had no involvement in the design, collection, analysis or interpretation of data; or in the writing and submission of the manuscript.
Competing interests None.
Ethics approval Ethics committee approval from Mount Sinai Hospital, Toronto, Ontario, Canada.
All authors meet criteria for authorship, participated in the writing of the manuscript, and have seen and approved the submitted version.