Improved Reliability of Measurement of Lactate Dehydrogenase by IFCC Method in Heparin Plasma

Abstract

Our laboratory recently reported (1) an excessively high frequency of duplicate errors in measurements of lactate dehydrogenase (LD; l-lactate:NAD+ oxidoreductase; EC 1.1.1.27) activity with the Roche IFCC-recommended method (2). This unacceptably high frequency of duplicate errors was found with various Hitachi analyzers (Roche GmbH) with primary lithium-heparin tubes with plasma separator from Becton Dickinson but not with serum or EDTA plasma. Such duplicate errors were not seen with the German- and French-recommended LD methods (3)(4), nor were such duplicate errors seen when nonevacuated heparin tubes from Sarstedt were used (5). In addition to the effects of methods, we investigated the effects of sample preparation, method modifications, mixing procedures, and the use of different lithium-heparin-containing tubes with and without plasma separator, lithium-heparin glass and plastic tubes, different lithium-heparin concentrations, and subsampling into secondary tubes. The results of all of these experiments are shown in Table 1 of the Data Supplement that accompanies the online version of this Technical Brief at http://www.clinchem.org/content/vol51/issue1/. Previously, we showed that the high frequency of duplicate errors was not caused by carryover from reagents for other tests and was not restricted to one specific type of Hitachi analyzer (1). In the present study, we demonstrate that the high frequency of duplicate errors is not restricted to the use of Roche reagents, confirming that the duplicate errors are caused by the combination of evacuated lithium-heparin tubes from Becton Dickinson …