Predictive value of modified ROX index for prognosis in patients with acute exacerbation of interstitial lung disease

Objective To explore the clinical predictive value of the early modified ROX (mROX) index for short-term prognosis in patients with acute exacerbation of interstitial lung disease (AE-ILD). Methods Retrospective analysis was performed on clinical data from AE-ILD patients(n=149) who were admitted to the Affiliated Hospital of Xuzhou Medical University from January 2022 to December 2024. According to their 28-day survival status, the patients were divided into two groups: a death group(n=65) and a survival group(n=84). General information and baseline data were collected, and their mROX indices at admission and 24 h after admission were recorded. Univariate Cox regression analysis was conducted to screen potential risk factors. Furthermore, a multivariate Cox proportional hazards model was constructed to determine independent predictors of in-hospital mortality in AE-ILD patients. Restrictive cubic splines (RCS) were used to evaluate the relationship between mROX index and 28-day mortality in AE-ILD patients. Receiver operating characteristic (ROC) curves were plotted to investigate the predictive value of the mROX index for 28-day mortality and to calculate the optimal cutoff value. Kaplan-Meier survival curves were drawn for patients with different 24-hour mROX index levels. Results The mROX index at admission (6.8±3.6) and at 24 hours 5.2 (3.8, 6.5) in the death group were both significantly lower than those in the survival group (P<0.05). Multivariate Cox proportional hazards regression analysis showed that the mROX index at admission (HR=0.76, 95%CI: 0.71-0.81, P<0.05) and at 24 hours (HR=0.42, 95%CI: 0.34-0.52, P<0.05) were independent risk factors for 28-day mortality in AE-ILD patients. The area under the ROC curve for the 24-hour mROX index predicting 28-day mortality in AE-ILD patients was 0.940 (95%CI: 0.921-0.957, P<0.05), with an optimal cutoff value of 8.89. RCS analysis revealed a nonlinear positive correlation between the 24-hour mROX index and the risk of in-hospital mortality in AE-ILD patients (P<0.05). When the 24-hour mROX index was >8.89, the risk of death significantly decreased with increasing mROX index (nonlinear test P<0.001). Conclusions A decrease in the 24-hour mROX index is associated with an increased 28-day mortality in AE-ILD patients. The 24-hour mROX index has good predictive value for 28-day mortality in these patients.