Predicting Survival Across Acute Exacerbation of Interstitial Lung Disease in Patients with Idiopathic Inflammatory Myositis: The GAP-ILD Model

Introduction: Risk prediction is challenging in patients with idiopathic inflammatory myopathies (IIM) and acute exacerbation of interstitial lung disease (AE-ILD) because of heterogeneity and patient-specific variables. Our objective was to assess whether mortality is accurately predicted in patients with IIM and AE-ILD by using the gender age physiology ILD (GAP-ILD) model, a clinical prediction model that was previously validated in patients with idiopathic pulmonary fibrosis. Methods: A retrospective cohort study was conducted in the First Affiliated Hospital, Zhejiang University, wherein 60 consecutive patients with IIM and AE-ILD admitted between February 2011 and April 2019. The GAP-ILD was assessed retrospectively on the basis of gender, age and pulmonary function test. Results: Patients with AE-ILD (n = 60) were identified and collected, 26 deaths occurred during follow-up, and the non-survivors group presented a higher level of GAP-ILD index (P = 0.005), bacterial infection (P = 0.013), and myositis disease activity assessment (MYOACT) (P = 0.031). The subsequent multivariate logistic regression analysis of overall mortality in AE-ILD revealed that bacterial infection (OR 5.275, P = 0.037) and GAP-ILD index (OR 2.292, P = 0.011) conferred significant risk of mortality. The GAP-ILD index was able to separate patients with AE-ILD into two groups with a statistically significant difference in survival rate (log rank P = 0.002). Satisfactory mortality estimation was maintained in the corresponding GAP-ILD index across the AE-ILD group. Conclusion: The GAP-ILD model preforms well in risk prediction of mortality among patients with IIM and AE-ILD. Pulmonary bacterial infection can also be taken as an initial predictor of poor prognosis in patients with IIM and AE-ILD that must be taken seriously.