The Refractory DermatoMyositis Index (ReDMI): a clinical tool to predict refractory disease in patients with...

To prospectively address the predictive features of refractory dermatomyositis (DM) and to construct and internally validate a clinical predictive index to timely identify patients at risk of this complication.

We recruited 168 patients with DM in a tertiary care centre in Mexico, and prospectively followed them, looking for the primary outcome, which was the diagnosis of refractory disease, defined as persistent disease activity three months after an adequate treatment course with glucocorticoids and at least one immunosuppressant. A logistic regression analysis was performed to calculate the odds ratios (OR) with 95% confidence interval (95% CI) of each predictive feature and to construct the Refractory DermatoMyositis Index (ReDMI).

One hundred twenty-one (72%) patients were women, and the most frequent myositis-specific antibody was Mi2 (23.9%). Fifty-seven patients (33.9%) developed refractory disease. The positivity for anti-TIF1-g (3.76 (1.17-13.3), p=0.029), the gastrointestinal disease activity (visual analogue scale) (1.11 (1.004-1.249), p=0.04), and alopecia (2.5 (1.11-5.7), p=0.026) were the refractoriness predictive factors. ReDMI predicted refractory disease with an OR of 3.57 (95% CI 1.71-7.59), an optimism corrected area under the curve of 0.67 with good internal validity and calibration.

After external validation, the ReDMI may be a useful clinical tool to timely detect DM patients at risk of developing refractory disease who may be candidates to receive an early more aggressive therapy.