Comorbidity of PaO2/FiO2 and nonthyroidal illness syndrome synergistically predicts 28-day mortality in sepsis: A retrospective cohort study from the MIMIC-IV database.

ObjectiveThis study explores the prognostic value of combining the PaO₂/FiO₂ ratio and nonthyroidal illness syndrome (NTIS) for predicting 28-day mortality in patients with sepsis.MethodsA retrospective cohort study was conducted using data from adult sepsis patients admitted to the ICU in the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Patients were divided into four groups based on PaO₂/FiO₂ ratio levels and the presence of NTIS (Groups 1-4). Kaplan-Meier (K-M) analysis with the log-rank test was used to compare 28-day mortality among groups. Multivariate Cox regression was performed to evaluate the independent association between group classification and mortality. A restricted cubic spline (RCS) was used to explore the relationship between PaO₂/FiO₂ ratio and 28-day mortality.ResultsA total of 599 sepsis patients were included in the analysis. Among the four P/F-NTIS stratified groups, Group 4 (P/F ≤ 200 mmHg with NTIS) exhibited the highest 28-day mortality rate (37.11%), significantly higher than Groups 1, 2, and 3 (p < .001). K-M analysis revealed a significantly lower survival probability in Group 4 (log-rank test, p < .001). Univariate Cox regression analysis identified P/F-NTIS classification as significant predictors of 28-day mortality. Multivariate Cox regression analysis confirmed that Group 4 was independently associated with increased 28-day mortality (HR = 1.70, 95% CI [1.08-2.69], p = .022). RCS analysis showed a nonlinear but statistically significant association between P/F ratio and 28-day mortality (p for nonlinearity = .242), further supporting the prognostic relevance of oxygenation status.ConclusionThe combined evaluation of the P/F and NTIS provides a more comprehensive risk stratification approach, allowing for improved 28-day mortality prediction in septic patients.