Background: Calprotectin is an acute-phase inflammatory protein that is released from the Polymorphonuclear leucocyte (PMNL). Calprotectin is used clinically widespread in the diagnosis and monitoring treatment of inflammatory bowel disease. The aim of this work was to assess the value of ascitic calprotectin as a diagnostic marker of spontaneous bacterial peritonitis (SBP).

Methods: This cross-sectional laboratory-based study was carried out on 50 patients, diagnosed with cirrhotic ascites without clinical or laboratory evidence of SBP for group 1 and diagnosed with cirrhotic ascites with SBP for group 2. SBP was diagnosed by positive ascitic fluid bacterial culture, an increase in polymorphonuclear leukocytes white blood cells (WBCs) (PMNLs) count in ascites (>250 cells/mm3) and without any intra-abdominal source of infection.

Results: : Protein, serum ascites albumin gradient (SAAG), PMNL and calprotectin were significantly elevated in the SBP group compared to non-SBP group (P < 0.001). The cut off point value of calprotectin 5.045 showed 89% sensitivity and 86% specificity (P-value <0.001). In multilinear regression, PMNL, and calprotectin were significant predictors of SBP (P ≤ 0.05).

Conclusions: Ascitic calprotectin was significantly higher in the SBP group than the non-SBP group and correlates well with the gold standard for diagnosing SBP, which is PMNLs of 250 cells/mm3 or more. This means that it can be used as a reliable and satisfactory diagnostic marker for diagnosing SBP with high accuracy. Also, the level of ascitic calprotectin is correlated with the severity of liver disease.