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

Abstract

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<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 > 18.28 significantly 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.