# Mortality prediction in geriatric ICU patients with pneumonia-related sepsis: APACHE II, NEWS, and serum lactate

## TL;DR

This study finds that APACHE II and NEWS scores are strong predictors of mortality in older ICU patients with pneumonia-related sepsis, while lactate adds limited value.

## Contribution

The study evaluates the combined use of APACHE II and NEWS scores for mortality prediction in geriatric sepsis patients.

## Key findings

- APACHE II and NEWS scores were strong independent predictors of mortality in geriatric ICU patients with pneumonia-related sepsis.
- Serum lactate did not independently predict mortality but improved a baseline model's discrimination when combined with clinical-laboratory data.
- The APACHE II+NEWS model achieved the highest discrimination (AUC 0.85) for predicting mortality.

## Abstract

Sepsis secondary to pneumonia is a prominent cause of intensive care unit (ICU) admissions and mortality among older adults, yet early bedside risk stratification poses significant challenges. This study aimed to evaluate the predictive value of the Acute Physiology and Chronic Health Evaluation II (APACHE II) and the National Early Warning Score (NEWS), both individually and in combination, alongside admission serum lactate levels, for predicting mortality in geriatric ICU patients with pneumonia-related sepsis. In this single-center retrospective cohort study, we analyzed patients aged 65 years and older who were admitted between January 1, 2020, and July 1, 2025. Sepsis was defined according to Sepsis-3 criteria; APACHE II (using the worst values within the first 24 hours) and NEWS (measured at ICU admission) were recorded, along with the first lactate and other biomarkers obtained within the first 24 hours. We assessed mortality predictors using logistic regression and evaluated model discrimination through receiver operating characteristic (ROC) analysis. Among the 179 patients (median age 80), the ICU mortality rate was 64.8%. Non-survivors exhibited significantly higher APACHE II and NEWS scores, as well as elevated lactate and inflammatory markers (all P < 0.001). In multivariable analysis, APACHE II (OR 1.130; P < 0.001), NEWS (OR 1.239; P ═ 0.003), and a history of stroke (OR 2.856; P ═ 0.041) were identified as independent predictors of mortality, whereas lactate did not demonstrate independent predictive capability. Although lactate improved the discrimination of a baseline clinical-laboratory model (AUC increased from 0.67 to 0.75), it offered no incremental benefit when APACHE II and NEWS were included; the combined APACHE II+NEWS model achieved the highest AUC of 0.85. Exploratory cut-offs identified very high-risk subgroups (APACHE II >21 with NEWS >8 or lactate >2 mmol/L), with mortality rates approximating 86%–87%. In conclusion, APACHE II and NEWS are robust early predictors of mortality in geriatric patients with pneumonia-related sepsis, while lactate may assist in early risk stratification but provides limited prognostic value beyond these scoring systems.