Objective To explore the correlation between the nutritional and immunity score (NIS) based on prealbumin and T lymphocyte count and the prognosis of critically ill patients.

Methods A retrospective study was conducted involving patients from the intensive care unit of the First Affiliated Hospital of Zhengzhou University from September 2020 to August 2021. Patients’ basic information, Acute Physiology and Chronic Health Evaluation Ⅱ (APACHE Ⅱ) scores within 24 hours of admission, and relevant biochemical indicators were collected. The primary endpoint was all-cause mortality within 28 days. The optimal cut-off values for prealbumin and T lymphocyte count related to mortality risk were determined using X-tile software. Patients were stratified according to these cut-off values and normal reference ranges, and the NIS was calculated. Univariate and multivariate Cox regression analyses were conducted to evaluate the relationship between NIS and mortality.

Results The optimal cut-off value for prealbumin was 110 mg/L, and for T lymphocyte count, it was 455/μL, with NIS scores ranging from 0 to 4. After adjusting for confounding factors, patients with NIS scores of 2 (HR＝1.87, 95%CI 1.19-2.94, P＝0.023), 3 (HR＝2.04, 95%CI 1.20-3.19, P＝0.007), and 4 (HR＝1.68, 95%CI 1.24-3.96, P＝0.005) showed a significantly increased risk of mortality.

Conclusions NIS≥2 is associated with an increased risk of death in critically ill patients. NIS can serve as an effective tool for early risk stratification and prognostic assessment in critically ill patients.