Validity of the disease activity score in undifferentiated arthritis

Abstract

Objective. To study whether the Disease Activity Score (DAS) is a valid measure of disease activity in undifferentiated arthritis (UA). Methods. Data from a randomized, double-blind, placebo-controlled trial of methotrexate (MTX) and placebo involving 110 patients with UA were used. Data included baseline and 3, 6, 9, and 12 months, as well as diagnosis at 18 months. Validity of the DAS was analyzed using factor analysis, correlations with disease activity variables, correlations with changes in disability and joint damage, differences in DAS between diagnoses, and detecting the difference between placebo and MTX. Results. Three disease activity factors were retrieved from the disease activity variables: patient reported outcomes, tender and swollen joints, and acute phase reactants. The DAS had its highest correlations (r > 0.77) with tender joint counts, followed by swollen joint counts (r > 0.63) and patient reported outcomes (r > 0.30), but the DAS correlated less with C-reactive protein levels (r ‫؍‬ 0.32). Over time, the DAS was related to the Health Assessment Questionnaire response with an odds ratio of 4.1 (95% confidence interval 2.1-8.0), but not with change in joint damage. At 18 months, the mean DAS was 2.6 for rheumatoid arthritis patients, 2.2 for UA patients, and 1.9 for patients in remission (P ‫؍‬ 0.001). The DAS discriminated better than all single variables between MTX and placebo, with a Guyatt's effect size of 0.89. Conclusion. The DAS appears to be a reasonably valid measure of disease activity for use in UA clinical trials.

The Scottish Early Rheumatoid Arthritis (SERA) Study: an inception cohort and biobank

“…There is significant phenotypic overlap between RA and UA, therefore we chose to initially analyse the outcomes as a combined cohort, since in practice many clinicians treat both conditions based upon the same principles, though this may have skewed the findings. A previous study suggests that the DAS28 may be a valid outcome measure in UA [34], but the performance of the SDAI has not yet been validated. The study also has other limitations: as a research study, the patients that agree to participate may differ from those that decline; patients were recruited soon after diagnosis but nonetheless baseline clinical and laboratory findings may already have been altered by prior treatment in primary care.…”

Development and Validation of a New Disease Activity Index as a Numerical Sum of Four Variables in Patients With Early Arthritis

“…This approach is consistent with the current trend of early management and diagnosis of RA that led to the development of the new ACR/EULAR 2010 classification criteria (37). To our knowledge, only one other publication has tried to address the validation of DAS in UA (38). Our group is performing an additional validation in longstanding disease.…”

Monitoring rheumatoid arthritis

“…DAS, DAS28, SDAI and CDAI also have validity in undifferentiated arthritis [30] and psoriatic arthritis, although for the latter an index similar to the SDAI and CDAI, the DAPSA, may have better utility and validity [31].…”