To identify predictors of response to immunosuppressive therapy after one year, with a focus on autoantibodies, in patients newly diagnosed with idiopathic inflammatory myopathies (IIM) followed longitudinally in an electronic registry.
We assessed the association between autoantibody-defined groups and improvement according to ACR/EULAR 2016 response criteria.
We identified 156 patients; of them, 111 patients (71%) were positive for any autoantibody tested, 90% received glucocorticoid treatment at baseline, and 78% received immunosuppressive drugs at some follow-up point. After one year from the index date, the overall median improvement score was 27.5 (IQR 10-51). No differences were observed in the total improvement score between the autoantibody-defined groups. Sixty-two percent of patients (n = 96) showed a minimal response, 38% (n = 60) achieved a moderate response, and 19% (n=30) achieved a major response. Regarding the different levels of response, DM-specific autoantibodies were associated with a moderate response versus the seronegative group (reference), OR 4.12 (95% CI 1.2-16.5). In addition, dysphagia, time from symptom onset to diagnosis, and initial glucocorticoid dose were significant predictors of response after one year of follow up.
Patients with DM-specific autoantibodies achieved better levels of response compared to other autoantibody-defined groups. Dysphagia, shorter time span from symptom onset to diagnosis and intensive initial immunosuppressive treatment were associated with a higher response rate after one year of pharmacological treatment from the index date, regardless of autoantibody status.