Objectives: To establish the value of a modified Disease Activity score with Optical Spectral Transmission score (DAS-OST) without joint counts but with a HandScan score, versus that of DAS28, to classify rheumatoid arthritis (RA) as active versus inactive, with as reference standard the rheumatologist's clinical classification.
Methods: RA patients with at least one HandScan and DAS28 measurement performed at the same visit were included. Data was extracted from medical records, as was the clinical interpretation as active or inactive RA by the rheumatologist. Logistic regression analyses were performed to calculate areas under the receiver operating characteristics (AU-ROC) curves. The clinical interpretation was used as reference standard in all analyses, and disease activity measures were used as predictor variables. The performance of predictor variables (AU-ROCs) was compared.
Results: The data of 1505 RA patients were used for analyses. The highest AU-ROC of 0.88 (95%CI 0.85-0.90) was shown for DAS28; AU-ROC of DAS-OST was 0.78 (95%CI 0.75-0.81), difference 0.10, p<0.01.
Conclusions: Compared to DAS28, DAS-OST classified RA statistically significantly less well as active versus inactive, when using the clinical classification as reference standard. However, a DAS-modification without joint scores might have a place in strategies limiting routine outpatients' visits to the rheumatologist.