Higher NLR Values Can Predict Gram-Negative Spontaneous Bacterial Peritonitis and a High In-Hospital Mortality Rate in Patients with Spontaneous Bacterial Peritonitis

Background: Spontaneous bacterial peritonitis (SBP) represents a significant complication of liver cirrhosis; Gram-positive bacteria (GPB) predominance was recently noted in some areas, with increased antibiotic resistance. Etiology and mortality prediction are important in culture-negative SBP and for empirical antibiotherapy before the arrival of culture results. Methods: A retrospective study was performed on patients with cirrhosis and ascites admitted between 2018 and 2024, divided into culture-positive SBP (Gram-positive and Gram-negative), culture-negative SBP, and non-infected ascites. The NLR (neutrophil-to-lymphocyte ratio) accuracy for the prediction of SBP and in-hospital mortality was estimated using ROC analysis. Results: Overall, 45 culture-positive SBP, 28 culture-negative SBP, and 600 control ascites were diagnosed; Gram-positive SBP represented 60%; median NLR values were significantly higher in patients with Gram-negative compared with Gram-positive SBP (8.79 in Gram-negative versus 3.92 in Gram-positive SBP, AUC 0.752, p = 0.003); and a limited role in SBP prediction was recorded (AUC 0.642, p = 0.003), with no difference between culture-positive and culture-negative SBP. The NLR median values were higher for patients who died in hospital in all patients with cirrhosis, in SBP, and culture-positive SBP, but not in culture-negative SBP. Conclusions: Higher NLR values were associated with Gram-negative SBP etiology and with in-hospital mortality in all cirrhosis, in SBP, and especially in culture-positive and Gram-negative SBP cases. High NLR values can predict the Gram-negative etiology in patients with an ascitic neutrophil count above 250/mm3, which can be used to guide empirical antibiotherapy until cultures are available or in culture-negative SBP.