To investigate the results and feasibility of available scales to measure minimal disease activity (MDA) and remission in rheumatoid arthritis (RA) in the clinic.
We studied 849 consecutive patients with RA seen in a community rheumatology practice for routine RA care by 4 rheumatologists, beginning in March 2007 and ending in August 2007. Patients and physicians completed a simple form at each visit. We calculated the Disease Activity Score 28 (DAS28), Clinical Disease Activity Index (CDAI), physician assessment of global activity, and the Patient Activity Scale (PAS-II). From these we calculated remission and MDA prevalence in this community practice.
The DAS28 could not be determined in more than 50% of patients because of referring physician and insurance company restrictions. Remission prevalences differed by assessment method: DAS28 28.5%, CDAI 6.5%-8.1%, physician global 12.5%, PAS 13.7%. MDA was 26.9% using the American College of Rheumatology core set variables, 34.7% using the DAS28, and 26.8% using the PAS-II. The kappa statistic was only fair (0.2 to 0.4) for most comparisons between assessment methods. No significant differences were noted for remission and MDA according to biologic therapy.
The CDAI and/or physician global and PAS-II are simple acceptable ways to measure RA activity in the clinic, but results differ strikingly according to method. Further standardization appears to be required for full implementation of the CDAI. Caution is urged before using these methods for regulatory purposes.