The influence of anticoagulants on the measurement of total protein concentration in equine peritoneal fluid

The aim of this study was to evaluate the influence of two commonly used anticoagulants (K 3EDTA and lithium heparin) on refractometric and spectrophotometric measurement of total protein (TP) concentration in equine peritoneal fluid samples. The influence of a commercial solution of K 3EDTA, a solution of K 3EDTA in distilled water and lithium heparin on the refractometric and spectrophotometric (biuret) quantification of TP content in peritoneal fluid samples was assessed. Total protein concentration measured by refractometry was consistently overestimated in samples with commercial K 3EDTA. The solution of K 3EDTA in distilled water only caused TP overestimation at high K 3EDTA concentrations (>5 μmol/ml). By contrast, lithium heparin did not influence the refractometric values of TP. Neither anticoagulant modified TP values when measured by the biuret method. In conclusion, the use of K 3EDTA as anticoagulant may result in a significant overestimation of TP values of peritoneal fluid samples measured by refractometry.