Potential source of heterogeneity included the different characteristics of the studies, such as methodological quality, admission category, size of the study populations, different reference standards in PD or cirrhotic patients for peritonitis (ascitic PMN > 50/mm3 or > 250/mm3, respectively), different countries and different human race and different methods used for measurement of PCT (LUMItest, ECLIA and the Semi-quantitative PCT-Q assay systems). Here, CALCA is linked to peritonitis.