The ratio of calprotectin to total protein as a diagnostic and prognostic marker for spontaneous bacterial peritonitis in patients with liver cirrhosis and ascites

Background: Diagnosis of spontaneous bacterial peritonitis (SBP) is based on a differential ascites leukocyte count which does not provide prognostic information. We performed a pilot study to assess calprotectin in ascites as an alternative diagnostic and prognostic marker. Methods: We collected ascites from patients with liver cirrhosis from March 2012 to July 2013. Routine clinical and laboratory data of the patients were recorded. Ascites calprotectin levels were determined by ELISA. Results: Overall, we collected 120 ascites samples from 100 patients with liver cirrhosis and from eight patients with malignant peritoneal effusion as disease control. Samples without infection had significantly lower calprotectin levels (median 34 ng/mL, range 5-795) than SBP samples (median 928 ng/mL, range 21-110,480; p<0.001) and malignant effusions (median 401, range 47-2596 ng/mL; p<0.001). In non-infected ascites, calprotectin levels were higher in Child-Pugh stage B versus C (median 57 ng/mL vs. 17 ng/mL; p<0.001) and in alcoholic versus viral cirrhosis (median 37 ng/mL vs. 10 ng/mL; p=0.015). The ratio of ascites calprotectin to total protein was a better marker for SBP than calprotectin alone (AUROC=0.93; p<0.001; sensitivity 93%, specificity 79%; positive predictive value 60%; negative predictive value 97%). In addition, high levels of the ratio to total protein were associated with poor 30-day survival (p=0.042). Conclusions: The ratio of ascites calprotectin to total protein may be a promising new diagnostic and prognostic marker in patients with liver cirrhosis and SBP and should be evaluated further.