Maxime Verhoeven

204 Chapter 11 ABSTRACT Objective To establish the value of a modified DAS (DAS-OST) without joint counts but with a HandScan score (OST), versus that of DAS28, to classify 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 Data of 1505 unique 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. When removing OST-score from DAS-OST, AU-ROC decreased from 0.78 to 0.77. Conclusion Compared to DAS28, DAS-OST classified RA statistically significantly less well as active versus inactive, when using the clinical classification as reference standard. The contribution of the OST-score to DAS-OST was negligible in this setting.