Early diagnosis of bloodstream infections by Neutrophil-Reactive Intensity (NEUT-RI): a retrospective analysis

Bloodstream infections (BSIs) are serious conditions caused by the presence of microorganisms in the blood. Although blood culture remains the diagnostic gold standard, it is time-consuming. Neutrophil activation plays a central role in the early immune response to infection and can be quantified using the Neutrophil-Reactive Intensity (NEUT-RI) parameter, derived from hematological analyzer using the fluorescence flow cytometry technology. The purpose of this study is to evaluate NEUT-RI as an early marker of BSI and compare its diagnostic performance with standard infection biomarkers. We conducted a retrospective study involving 120 inpatients with documented BSI. Each inpatient underwent blood testing for PCT (Procalcitonin), serum CRP (C-Reactive Protein), WBCs (White Blood Cells), neutrophil absolute count within 12 h prior to blood culture sampling. NEUT-RI values were retrieved from the complete blood count. A control group of 52 inpatients with negative blood cultures was also analyzed. Median NEUT-RI was significantly higher in BSI patients than in controls (53.43 FI vs 48.65 FI; p < 0.001). ROC (Receiver Operating Characteristic) curve analysis showed an AUC (Area Under the Curve) of 0.785 for NEUT-RI, with 72.5% sensitivity and 76.9% specificity at a cut-off of 50.7 FI. Only Procalcitonin (AUC 0.882) outperformed NEUT-RI (p = 0.01). Our findings suggest that NEUT-RI increases in the early stages of bacteremia and may serve as a useful early indicator of bloodstream infection. NEUT-RI could be integrated into multi-parametric diagnostic algorithms to improve early detection of BSIs. Further studies are warranted to validate these preliminary results.