Objective: A model to predict progression from undifferentiated arthritis (UA) to RA was recently created. This study aimed to validate the model in a Canadian UA cohort.
Methods: The prediction rule consists of variables, which are scored (range 0-13), with higher scores reflecting an increased risk of RA. The model was applied to baseline characteristics of all UA patients. Progression to RA was determined at 6 months.
Results: Overall, 105 patients were identified. By 6 months, 80 (76%) developed RA while 25 (24%) developed another diagnosis. The number of tender and swollen joints, RF positivity, anti-CCP positivity, poor functional status and high disease activity were associated with development of RA (p < 0.01). Among progressors, the median prediction score was 8.0 while non-progressors had a median score of 5.0. Using these cutoffs, 18 (72%) patients with scores ≤ 5 did not develop RA while 35 (97%) of patients 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, validating the original prediction model. Future research should focus on how to predict disease outcome and response to therapy among patients with intermediary scores.
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