BACKGROUND: In recent years, the hemoglobin, albumin, lymphocyte, and platelet (HALP) score has emerged as a potential marker of immunological and nutritional status. This study aimed to evaluate the association between the HALP score and prognosis in patients with sepsis. METHODS: This retrospective cohort study analyzed sepsis patients using clinical data from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Patients were classified into Low-score and High-score groups. Confounding factors were controlled through propensity score matching (PSM) analysis. The primary outcome was 28-day mortality in individuals with sepsis. Survival probabilities between groups were compared using Kaplan-Meier curves. Multivariable Cox regression analysis and a smoothing spline fitting curve were employed to investigate the relationship between the HALP score and 28-day mortality. ROC curve analysis and subgroup analysis were performed to evaluate the predictive ability of the HALP score and its components. RESULTS: A total of 2,968 sepsis patients were included, with 809 (27.26%) deaths within 28 days. After PSM analysis, the High-score group had a 24% lower risk of 28-day mortality compared to the Low-score group (HR, 0.76
95% CI, 0.64-0.91). In the unmatched cohort, the multivariable Cox regression model also indicated that the High-score group had a lower 28-day mortality risk (HR, 0.78
95% CI, 0.67-0.91). The smoothing spline fitting curve showed a nonlinear relationship between the HALP score and 28-day mortality, with an inflection point at 24.69. When the HALP score was below 24.69, an increase of one point in the HALP score was associated with a 2% reduction in 28-day mortality (HR, 0.98
95% CI, 0.97-0.99). The HALP score provided incremental predictive value for 28-day mortality when combined with the SOFA score. Albumin was identified as the most influential component of the HALP score. CONCLUSION: Among patients with sepsis, the HALP score exhibited a nonlinear relationship with 28-day mortality. An elevated HALP score is associated with reduced 28-day, 90-day, 360-day, and in-hospital mortality among sepsis patients.