A study using data from the MIMIC-IV database investigated the prognostic value of the Neutrophil-Platelet Activity Ratio (NPAR) in critically ill adult patients admitted to the ICU with a first acute myocardial infarction (AMI, or heart attack).

NPAR Linked to Higher Mortality: The study included 928 AMI patients and found that a higher NPAR (calculated within 24 hours of ICU admission) was consistently associated with older age, greater illness severity, and significantly higher all-cause mortality at all time points ($p < 0.001$). Survival Differences: Kaplan–Meier analysis confirmed that patients in the higher NPAR quartiles had significantly poorer survival outcomes (log-rank p < 0.0001$). Predictive Value: While NPAR’s predictive significance was slightly diminished in the most fully adjusted model (HR = 1.01, p = 0.055), it still demonstrated value for risk stratification.

Model Performance: Among the machine learning models tested, Logistic Regression showed the best predictive performance with an AUC of 0.740.

Nonlinear Effect: SHAP analysis revealed a complex, nonlinear effect of NPAR, where its impact on mortality was strongest at intermediate levels, and this contribution was influenced by the patient’s age.

Elevated NPAR is associated with increased mortality in critically ill AMI patients. As a readily available and low-cost biomarker, NPAR has the potential to aid in early risk stratification, though further prospective validation trials are necessary.

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