Clinical utility of Neutrophil Lymphocyte Ratio (NLR) as a marker of Spontaneous Bacterial Peritonitis (SBP) in patients with cirrhosis-An exploratory study

Background and objective: The diagnosis of spontaneous bacterial peritonitis (SBP) is made by presence of ≥250 polymorphonuclear neutrophil (PMN)/mm3 in the ascitic fluid. Paracentesis despite being the gold standard has its inherent risks and complications. Blood neutrophil-lymphocyte ratio is a simple test for inflammation. Highly sensitive C reactive protein (hsCRP) is a marker of inflammation which is mainly synthesized by the liver. We aimed to evaluate clinical utility of NLR and hsCRP as less invasive tests for diagnosis of SBP.
Methods: Fifty cases of cirrhosis with ascites with SBP and 50 age and sex matched controls of cirrhosis with ascites without SBP were enrolled for the study. NLR was calculated and hsCRP value was determined in both the groups and compared using independent t test. The sensitivity and specificity of NLR was estimated as a test for SBP diagnosis by using receiver operator characteristics (ROC) curve.
Results: NLR was found to be significantly higher in SBP patients (6.75 +/- 2.7) than those without it (2.81+/-1.06) with p value < 0.01. hsCRP was raised in both groups, 18.93+/-5.00 and 17.46+/-6.19 in cases and controls respectively, but there was no statistical difference between the two groups. For SBP diagnosis, a blood NLR > 3.38 had a sensitivity of 94% and a specificity of 80%.
Interpretation and conclusions: NLR could be used as a novel and less invasive test for diagnosis of SBP. hsCRP has a blunted rise in patients with cirrhosis with SBP and cannot be used as diagnostic marker.