Evaluation of A Novel Index That Incorporates Both Neutrophil-Lymphocyte Ratio and C-Reactive Protein for The Detection of Spontaneous Bacterial Peritonitis

Background: Diagnosing spontaneous bacterial peritonitis (SBP) requires a high clinical index of suspicion because the clinical presentation varies widely. Early detection and treatment of SBP are crucial for improving survival rates. Minimally invasive markers such as blood neutrophil-lymphocyte ratio (NLR) and serum C-reactive protein (CRP) could be helpful to clinicians in identifying SBP patients.
Objective: This study aimed to assess the diagnostic efficacy of integrating measurements of NLR and CRP as a minimally invasive approach for detecting SBP.
Patients and methods: This was a cross-sectional study that included 124 cirrhosis-related ascites patients admitted to the Alexandria Main University Hospital in the Department of Internal Medicine. Participants with ≥ 250 neutrophil cells/mm³ in ascitic fluid were defined as the SBP group (50 patients). In contrast, those with less than 250 neutrophil cells/mm³ in ascitic fluid and negative ascitic cultures were the non-SBP group (74 participants).
Results: There was a substantially elevated blood NLR and CRP in SBP patients (p < /em><0.001). Analyzed separately, NLR exceeding 3.16 offered a sensitivity of 76% and specificity of 97.3%, whereas CRP above 45.6 mg/L yielded a sensitivity of 84% and specificity of 91.8%. Our new index “NLR x √CRP” at a cutoff > 18.28significantly improved diagnostic precision, with a better sensitivity of 94.0% and specificity of 94.59%.
Conclusions: The use of “NLR x √CRP index” at a cutoff > 18.28 introduces an innovative, efficient, economical, and minimally invasive strategy for the diagnosis of SBP.