Quantitative CT analysis of interstitial pneumonia in anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis: a single center, retrospective study

Introduction This study aimed to assess the utility of quantitative high-resolution computed tomography (HRCT) for determining the clinical course of anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis-associated interstitial lung disease (MDA5 + ILD). Method This study retrospectively analyzed the data of 34 patients with MDA5 + ILD to determine the association between the clinical findings and extent of ILD via quantitative CT analysis at baseline and short-term follow-up. Quantified HRCT scores were evaluated as the lung severity score (LSS), percentage of opacity, and percentage of high opacity. Results Thirty-four patients underwent follow-up CT scans 35 (range: 14–78) days after diagnosis. Patients who died of rapidly progressive ILD had higher LSS ( p < 0.01), percentage of opacity ( p < 0.01), percentage of high opacity ( p = 0.01), total ground-glass opacity score ( p = 0.01), serum C-reactive protein (CRP) ( p = 0.03), and alveolar–arterial oxygen difference (Aa-DO2) ( p = 0.01) at follow-up than those who survived. Quantified HRCT scores correlated with serum CRP and Aa-DO2 levels at follow-up. LSS at follow-up (AUC = 0.844, p < 0.01) was the best predictor of death in MDA5 + ILD patients. Patients with an LSS of > 6.5 at follow-up had higher mortality than those with an LSS of ≤ 6.5, especially when receiving triple therapy. In multivariate analysis, an LSS of > 6.5 at follow-up was significantly associated with a poor outcome. Conclusions Quantitative CT analysis of MDA5 + ILD is useful for the objective assessment of respiratory status and disease activity. Short-term HRCT evaluation, particularly LSS, is most important in predicting its clinical course during triple therapy. Key Points • Quantitative CT analysis plays an important role in evaluating the clinical course of anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis-associated interstitial lung disease (MDA5 + ILD). • Quantified HRCT scores, particularly lung severity score, at short-term intervals from diagnosis can help to predict prognosis after triple therapy in MDA5 + ILD.