Delta neutrophil index discriminates true bacteremia from blood culture contamination

Delta neutrophil index (DNI) has been reported to be useful in the diagnosis of sepsis. We evaluated the role of DNI for differentiating true bacteremia from blood contamination and compared the DNI value with previously validated markers such as procalcitonin (PCT) and C-reactive protein (CRP).

The blood culture positive group was subdivided into true bacteremia (n=199) and contamination (n=158). The blood cultures were incubated in the BacT/Alert 3D (bioMérieux, Marcyl'Etoile, France) and BACTEC FX (Becton Dickinson, Sparks, MD, USA) systems for 5days. Data of complete blood cell count were collected from an automatic cell analyzer (ADVIA2120 Hematology System, Siemens Healthcare Diagnostics) to calculate DNI.

Concentrations for DNI, PCT, and CRP were significantly higher in the true bacteremia group. When the gram-positive and gram-negative infections were compared among true bacteremia, only PCT was increased significantly in GNB bacteremia. DNI levels were well correlated with PCT (r=0.564, P<0.0001) and CRP (r=0.344, P<0.001) using the Spearman test among the culture positive bacteremia. The area under the ROC curve was 0.75 for PCT, 0.69 for CRP, and 0.69 for DNI.

We demonstrated the usefulness of DNI in differentiating true bacteremia from contamination in patients with a positive blood culture.