Correlation between the frailty index derived from laboratory tests and 4-week all-cause mortality in critically ill patients with pneumonia.

PURPOSE: To assess whether the laboratory-based frailty index (Lab-FI) is associated with 28-day all-cause mortality in critically ill patients in the intensive care unit (ICU) with pneumonia in an attempt to identify an easily accessible frailty assessment tool for this vulnerable population.

METHODS

This was a retrospective analysis of 9229 patients from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database who were evaluated by the Lab-FI (33 laboratory/vital sign variables) and stratified into quartiles (Q1-Q4). Propensity score matching (PSM) and Cox proportional hazards models (adjusted for demographics and comorbidities) were used to assess the association between the Lab-FI and mortality. Harrell's C-index, integrated discrimination improvement (IDI), and net reclassification improvement (NRI), were used to evaluate the advantages of the Lab-FI over traditional severity scores. Kaplan-Meier and restricted cubic spline (RCS) analysis were used to compare mortality across different quartiles.

RESULTS

Of the 9229 patients, 2416 died within 28 days. Higher Lab-FI scores correlated with increased mortality (Hazard ratio (HR): 1.14 per 0.1-unit increase; 95% confidence interval (CI): 1.09-1.18, p < 0.001). Categorical analysis revealed a progressive elevation of mortality in Q2-Q4 vs. Q1 (p < 0.001 for trend). Subgroup analysis identified age and cerebrovascular disease as significant effect modifiers (interaction p < 0.05).

CONCLUSION

Lab-FI is a robust and objective biomarker for 28-day mortality risk stratification for patients with pneumonia in the ICU. Higher scores indicate a significantly elevated risk of mortality, particularly in high-risk subpopulations. Lab-FI provides an automated and objective tool for risk stratification that can be used to facilitate triage decisions and the allocation of intensive care resources, thus highlighting its utility in guiding clinical resource allocation and targeted interventions.