Impact of neutrophil percentage-to-albumin ratio on mortality in iron-deficiency anemia patients: a retrospective study using MIMIC-IV database

Background: In the intensive care unit (ICU), the incidence of iron-deficiency anemia (IDA) is relatively high and is associated with various adverse clinical outcomes. Therefore, it is crucial to identify simple and practical indicators to assess the mortality risk in ICU patients with IDA. This study aims to investigate the relationship between the Neutrophil Percentage-to-Albumin Ratio (NPAR) levels in patients with IDA in the ICU and their all-cause mortality at 30 and 365 days.

Materials and methods: We analyzed data from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) 3.0 database spanning the years 2008-2022 and identified a cohort of 817 patients with IDA who met our inclusion criteria. Through multivariate Cox regression analysis, the relationship between NPAR levels and 30-day and 365-day mortality risks was assessed, and restricted cubic splines (RCS) models were used to explore potential nonlinear relationships. Additionally, an inflection point analysis was conducted to evaluate the potential of NPAR levels in predicting short- and long-term mortality risks.

Results: The study found that high NPAR levels were significantly associated with an increased risk of 30-day and 365-day mortality in patients with IDA (hazard ratio [HR] range 1.49-2.23, p < 0.001 for all). The relationship between natural logarithmic transformation (ln) NPAR levels and 30-day and 365-day mortality risks exhibited an inverse "L" shaped pattern. Patient mortality risk increased significantly when ln-transformed NPAR levels exceeded 1.2 (HR range 3.366-4.304, p < 0.001 for all). Additionally, subgroup analyses did not reveal any significant interactions, indicating that the predictive effect of NPAR on mortality risk is relatively consistent across different subgroups.

Conclusion: We found an inverse "L" shaped relationship between ln-transformed NPAR levels and 30-day and 365-day mortality risks, particularly when ln-transformed NPAR values exceed 1.2, which is significantly associated with an increased risk of death within 30 and 365 days for patients.