Correlation between red cell distribution width to total calcium ratio and in-hospital mortality in patients with non-idiopathic pulmonary fibrosis interstitial lung diseases: A retrospective cohort study from the MIMIC-IV database

This study aims to investigate the potential of the red cell distribution width to total calcium ratio (RCR) as a biomarker for in-hospital mortality in patients with non-idiopathic pulmonary fibrosis (IPF) interstitial lung diseases. A retrospective cohort analysis was carried out utilizing the Medical Information Mart for Intensive Care database, including 1138 patients with non-idiopathic pulmonary fibrosis interstitial lung diseases. Patients were divided into a survivor group (n = 1023) and a non-survivor group (n = 115) based on in-hospital mortality. The Boruta algorithm combined with a machine learning-based random forest algorithm was employed to calculate Shapley Additive Explanations (SHAP) values to identify clinical indicators significantly contributing to in-hospital mortality. A nomogram model based on logistic regression was constructed to assess the relationship between RCR and in-hospital mortality. Compared to the survivor group, the non-survivor group's average age was significantly older (73.00 ± 10.67 years vs 69.83 ± 13.24 years, P = .013), and RCR was significantly elevated in the non-survivor group (1.83 ± 0.30 vs 1.73 ± 0.27, P