Diagnostic utility of plasma heparin-binding protein and procalcitonin among patients with bacterial infections: a single-center retrospective study

Objective This study aimed to evaluate the discriminatory capacity of plasma heparin-binding protein (HBP), procalcitonin (PCT), and composite immune inflammatory indices in differentiating bacterial infections from non-infection states, as well as to explore their potential for Gram classification and severity stratification. Methods A single-center retrospective case-control study enrolled 65 patients with confirmed bacterial infection and 135 non-infected controls. Plasma HBP, PCT, and complete blood count-derived indices were measured from initial blood samples collected within 24 hours of admission. Group comparisons were performed using statistical tests, and diagnostic performance of each biomarker was evaluated using receiver operating characteristic curves. Results HBP levels were significantly higher in infected patients than in controls ( p < 0.001) and demonstrated the best discriminative performance among all markers (AUC = 0.86). Multivariable analysis identified HBP, monocyte, and lymphocyte count as independent predictors for Gram-positive infections, while HBP, PCT, and neutrophil count were associated with Gram-negative infections. Notably, HBP levels increased progressively from the non-infected group (19.45 ng/ml) to PCT-defined infection localized infection (35.13 ng/ml) and PCT-defined infection severe infection (111.95 ng/ml, p < 0.001), supporting its utility in PCT-defined severity stratification. Conclusion HBP is a promising biomarker for diagnosing bacterial infections, particularly Gram-negative infection, and for stratifying PCT-defined infection severity. However, given the exploratory nature of the Gram classification findings and the single-center retrospective design, these results require validation in larger prospective cohorts.