Dynamic prognostic nutritional index and 28-day mortality in sepsis: a joint modeling analysis

BACKGROUND: Although the Prognostic Nutritional Index (PNI) is associated with sepsis outcomes, admission values may primarily reflect acute illness severity. We examined whether longitudinal PNI provides prognostic value beyond baseline risk. METHODS: In this retrospective cohort study of 492 adults with sepsis, baseline PNI was assessed using Kaplan-Meier analysis and adjusted restricted cubic splines. A joint model was used to link repeated PNI measurements from days 1 to 7 with time to 28-day mortality while accounting for informative dropout due to death or discharge. Time-dependent Cox models were further used to compare dynamic PNI with albumin and total lymphocyte count. RESULTS: Baseline PNI showed a non-significant trend toward survival separation (log-rank p = 0.063) and was not independently associated with 28-day mortality after multivariable adjustment (p = 0.122). By contrast, dynamic PNI was independently associated with mortality in time-dependent analyses (HR 0.730, p = 0.032), whereas albumin and total lymphocyte count were not. Joint modeling likewise demonstrated a significant independent association between longitudinal PNI and mortality (HR 0.831, p < 0.001). CONCLUSION: Baseline PNI showed limited independent prognostic value, whereas longitudinal PNI provided additional prognostic information and showed modestly better predictive performance than its individual components.