Cellular content in plasma of Becton-Dickinson lithium-heparin tubes: cause of unreliable results in the IFCC-recommended lactate dehydrogenase method

Abstract

Background: Measurement of lactate dehydrogenase (LDH) with the International Federation of Clinical Chemistry (IFCC)-recommended method in plasma was reported unreliable with primary evacuated lithium-heparin tubes from Becton-Dickinson, despite adequate removal of platelets from the plasma by optimized sample preparation. In this study, the composition of the top layer of the heparin plasma was investigated in relation to these duplicate errors. Method: Microscopic evaluation of cytospin preparations of the top layer of the plasma was compared with the difference between duplicates in the IFCC-recommended LDH assay using a Hitachi 911 analyser. Results: Duplicate errors could not be explained by the presence of one of the individual cell types. In 16 samples with cellular aggregates absent, three did show duplicate errors; all three had a moderate amount of red blood cells present. Conclusion: The presence of cellular aggregates in the top layer of the plasma was the main determinant for the occurrence of the high frequency of duplicate errors in the IFCC-recommended LDH method.