Non-homogeneous separation of triglycerides, gamma-glutamyltransferase, C-reactive protein and lactate dehydrogenase after centrifugation of lithium-heparin tubes.

Background: Clinical chemistry testing is influenced by a variety of preanalytical variables, including sample preparation. The presence of a diluted plasma layer at the top of primary tubes containing plasma citrate has recently been reported. However, no indication is available so far on the potential non-homogeneous distribution of clinical chemistry analytes during centrifugation of primary tubes containing lithium-heparin as an additive. Methods: A total of 40 lithium-heparin plasma samples were collected from volunteers and immediately centrifuged. An aliquot was obtained from the upper 0.4 mL of plasma (upper aliquot), 1.0 mL of plasma was discarded, and a second aliquot (lower aliquot) was obtained from the remaining plasma. The concentrations of alanine aminotransferase, albumin, alkaline phosphatase, amylase, amylase pancreatic, aspartate aminotransferase, direct bilirubin, total bilirubin, blood urea nitrogen, calcium, chloride, cholesterol, C-reactive protein (CRP), creatin...