Preanalytical study concerning the influence of tube type and centrifugation conditions on the concentration of calprotectin in ascites.

Abstract

Introduction: Concentration of calprotectin in ascitic fluid has been proposed as the possible diagnostic marker for spontaneous bacterial peritonitis. This study aimed to choose the optimal preanalytical conditions for the determination of the concentration of calprotectin in ascitic fluid.

Materials and methods: Study was performed using 20 samples of ascitic fluid of inflammatory etiology. Number of total nucleated (TNC) and polymorphonuclear cells (PMN) were determined on Advia 2120i (Siemens Healthineers). Ascitic samples were collected into three tube types (K2EDTA, tubes with clot activator and Li-heparin tubes) and centrifuged under three different conditions (400xg, 1500xg and 3000xg 15 minutes). Concentration of calprotectin was determined using Bühlmann's turbidimetric assay and potassium and lactate dehydrogenase using standard laboratory methods on Atellica Solution (Siemens Healthineers). Data was evaluated by Friedman test and Spearman's correlation coefficient.

Results: The highest concentration of calprotectin was observed in red tubes with clot activator (centrifuged 1500xg 15 minutes; median 0.349 mg/L, IQR 0.094-1.129 mg/L) and the lowest in lavender tubes (centrifuged 3000xg 15 minutes; median 0.109 mg/L, IQR: 0.037-0.850 mg/L). Friedman test showed statistically significant difference between concentration of calprotectin in different preanalytical conditions (P < 0.001). According to the desirable biological variation criteria, differences in calprotectin concentration were clinically significantly different for different preanalytical conditions.

Conclusions: To determine the concentration of calprotectin in ascites, we suggest using a test tube with a red cap and centrifugation conditions of 1500xg 15 minutes which is consistent with the relevant national and international guidelines.