Classification of rheumatoid arthritis into active or inactive with a modified Disease Activity score, for future use as a treat-to-target tool, with a HandScan score replacing joint counts

Objective 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. Conclusion 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.