MDA5 score--A Novel Lung Computed Tomography Scoring Method for Anti-Melanoma Differentiation-associated Gene 5-positive Dermatomyositis

Abstract

Background: Anti-melanoma differentiation-associated gene 5 (MDA5)-positive dermatomyositis (DM)-associated interstitial lung disease (ILD) is a life-threatening disease with a 6-month mortality as high as 50%. Evaluation of pulmonary high-resolution computed tomography (HRCT) is crucial in the prognostic prediction. This study aimed to develop a novel CT visual scoring method for anti-MDA5 positive DM-ILD.Methods: A prospective cohort of hospitalized patients with anti-MDA5 positive DM-ILD was analyzed, and was further divided into a derivation dataset and a validation dataset. The primary outcome was the six-month all-cause mortality since the time of admission. Three components of baseline pulmonary CT images, i.e., ground glass opacity (GGO), consolidation and fibrosis were semi-quantitatively calculated in different lung lobes. The multivariable COX proportional hazards model was used to identify independent prognostic risk factors and corresponding coefficients, based upon which a scoring model was constructed. In addition, an artificial intelligence (AI) algorithm-based analysis and an idiopathic pulmonary fibrosis (IPF)-based scoring were conducted as comparators. The prediction accuracy of different methods was measured and compared by Harrell concordance index (C-index). Results: Overall, 173 eligible patients were included. A novel GGO and consolidation-weighted CT visual scoring model for anti-MDA5 positive DM-ILD, namely ‘MDA5 score’, was developed with C-index values of 0.80 (95%CI 0.75-0.86) in the derivation dataset (n=116) and 0.84 (95%CI 0.71-0.97) in the validation dataset (n=57), respectively. While, the AI algorithm-based analysis, namely ‘AI score’, yielded C-index 0.78 (95%CI 0.72-0.84) for the derivation dataset and 0.77 (95%CI 0.64-0.90) for the validation dataset. ‘MDA5 score’ outperformed and IPF-based scoring (‘IPF score’) with respect to discrimination and clinical usefulness.Conclusions: The novel derived ‘MDA5 score’ may serve as an applicable prognostic predictor for anti-MDA5 positive DM-ILD and facilitate further clinical trial design. The AI based CT quantitative analysis from COVID-19 provided a promising solution for ILD evaluation.