# Logarithmically transformed lactate-to-hemoglobin ratio demonstrates a threshold effect on 28-day mortality in sepsis: Analysis of the MIMIC-IV database

## TL;DR

This study finds that a new ratio of lactate to hemoglobin can predict sepsis mortality, with a clear threshold for increased risk.

## Contribution

The novel contribution is identifying a threshold effect of the logarithmically transformed lactate-to-hemoglobin ratio on sepsis mortality.

## Key findings

- Elevated Ln_LHR is independently associated with increased 28-day mortality in sepsis patients.
- A threshold effect at Ln_LHR: −0.625 significantly increases mortality risk.
- Minimum temperature partially mediates the association between Ln_LHR and mortality.

## Abstract

To investigate the association between logarithmically transformed lactate-to-hemoglobin ratio (Ln_LHR) and 28-day mortality in sepsis patients, addressing the critical need for reliable prognostic biomarkers in this high-mortality condition.

This retrospective cohort study analyzed 20725 adult sepsis patients from the MIMIC-IV database (2008–2019). The primary exposure was Ln_LHR calculated from measurements within 24 hours of ICU admission, while the primary outcome was 28-day all-cause mortality. Covariates included demographics, physiological parameters, severity scores, and interventions. We employed multivariable logistic regression and restricted cubic splines to identify potential non-linear relationships.Finally,mediation analysis was used to assess the factors affecting sepsis mortality in Ln_LHR.

Elevated Ln_LHR was independently associated with increased 28-day mortality after comprehensive adjustment (OR:1.43, 95% CI:1.35–1.52). We identified a significant threshold effect at Ln_LHR: −0.625, above which mortality risk increased dramatically (OR:3.812, 95% CI:3.131–4.642). Subgroup analyses revealed the predictive efficacy of Ln_LHR exhibited significant variation across various factors, including age, the utilisation of norepinephrine, and the severity score. Mediation analysis revealed that minimum temperature, as a potential mechanism linking Ln_LHR to 28-day mortality, accounted for 9.2% of the total association.

Ln_LHR may represent a promising, readily available prognostic biomarker for sepsis mortality risk stratification, with a clinically meaningful threshold effect. This composite marker integrates critical pathophysiological information and may enhance risk assessment and guide clinical decision-making in sepsis management.