The usefulness of serum delta neutrophil index for differentiating bacterial and viral meningitis in the emergency department

OBJECTIVE When managing patients with acute meningitis in an emergency department (ED), early diagnosis of the type of infection (bacterial or viral) considerably affects the clinical course and treatment because of the high mortality and morbidity associated with bacterial meningitis (BM). The serum delta neutrophil index (DNI), a new inflammatory marker, reflects the fraction of circulating immature granulocytes and is elevated in cases of bacterial infection. The objective of this study was to evaluate whether serum DNI can be used to differentiate between BM and viral meningitis (VM) in the ED. METHODS This retrospective, observational study included 104 consecutive patients (aged >18 years) diagnosed with acute meningitis from January 2012 to November 2014 in a regional emergency center. White blood cell and neutrophil counts, C-reactive protein level, and DNI were evaluated regarding their usefulness for differentiating BM and VM. RESULTS Serum DNI was not significantly higher in the BM group (n=12) than in the VM group (n=92) (0 [interquartile range, 0% to 2.73%] vs. 0 [interquartile range, 0 to 0%], P=0.057). However, the white blood cell count and C-reactive protein level were statistically higher in the BM group (P=0.034 and P=0.026, respectively). Serum DNI was not found to be a statistically useful differential diagnostic parameter (area under the curve, 0.628; 95% confidence interval, 0.438 to 0.818). CONCLUSION Currently, there is no evidence that the serum DNI aids in differentiating acute BM from acute VM in the ED.