Correlation of a Modified Disease Activity Score with the Validated Original Disease Activity Score in Patients with Juvenile Dermatomyositis

Objective Juvenile dermatomyositis (JDM) is a rare disease in children that is treatable, but patients may suffer from long-term effects of the disease. Clinical trials are needed to find better treatments for affected patients. Among validated tools for evaluating disease activity clinically is the disease activity score (DAS), but it is not routinely collected in all clinics. We developed a modified DAS (DAS_mod) which can be scored using data routinely collected by our clinical staff, and has been used in previous studies. This study’s objective was to determine if our DAS_mod correlates with the validated DAS in patients with JDM.

Methods In this study, we used DAS_mod (scored 0-12) and DAS scores (scored 0-20) for patients with JDM in our clinic. We analysed the correlation between the DAS_mod and the validated DAS.

Results For 51 patients seen in our JDM clinic, the median (IQR) DAS_mod score was 2.0 (0, 4.0) and the median (IQR) DAS score was 3.0 (0, 5.5). Scores on the two tools were highly positively correlated (r = 0.94, p < 0.001, 95% CI [0.89, 0.96]). The linear regression was significant (R2 = 0.88, F (1, 49) = 357.60, p < 0.001) and in this dataset, the tools can be used interchangeably with the regression equation: DAS score = -0.26 + 1.5*DAS_mod.

Conclusion If the regression equation from this dataset is successfully tested against future datasets, then further research collaborations between centres that collect different data related to disease activity in children with JDM will be facilitated.