Use of the Delta Neutrophil Index as a Prognostic Factor of Mortality in Patients with Spontaneous Bacterial Peritonitis: Implications of a Simple and Useful Marker

BACKGROUND: Spontaneous bacterial peritonitis (SBP) is a common and life-threatening infection in patients with advanced cirrhosis. The prognostic value of a novel marker, the delta neutrophil index (DNI), was investigated relative to mortality in patients with SBP. MATERIALS & METHODS: Seventy-five patients with SBP were studied from April 2010 to May 2012. DNI at initial diagnosis of SBP was determined and compared with 30-day mortality rates. RESULTS: Of the patients, 87.7% were men, and the median age of all patients was 59.0 yrs. The area under the receiver-operating characteristic (ROC) curve of DNI for 30-day mortality was 0.701 (95% confidence interval [CI], 0.553–0.849; p = 0.009), which was higher than that of C-reactive protein (0.640, 95% CI, 0.494–0.786; p = 0.076) or the model for end-stage liver disease score (0.592, 95% CI, 0.436–0.748; p = 0.235). From the ROC curve, with the sum of sensitivity and specificity, the cutoff value of DNI was determined to be 5.7%. In the high-DNI group (DNI ≥5.7%), septic shock and 30-day mortality were more prevalent compared with the low-DNI group (84.2% vs. 48.2%, p = 0.007; 57.9% vs. 14.3%, p<0.001, respectively). Patients with an elevated DNI had a higher risk of 30-day mortality compared with those with a low DNI (4.225, 95% CI, 1.631–10.949; p = 0.003). CONCLUSION: A higher DNI at the time of SBP diagnosis is an independent predictor of 30-day mortality in patients with SBP.