This question is derived from the journal article “The Transition from Gel Separatory Serum to Lithium Heparin Gel Tubes in the Clinical Laboratory,” written by Oguzhan Zengi. The journal elaborated on the importance of switching to lithium heparin gel tubes in most clinical chemistry and immunoassay tests due to improved sample quality and decreased turnaround time (TAT) in the emergency laboratory.
As mentioned by the authors of a journal titled “The transition from gel separatory serum to lithium heparin gel tubes in the clinical laboratory” the reason for a negative bias for LDH was not fully understood. However, it is believed that LDH may be released from platelets and other cells into plasma during centrifugation. However, as claimed by Peake, M. J., Pejakovic, M., Alderman, M. J., Penberthy, L. A., and Walmsley, R. N., in a journal article titled “Mechanism of platelet interference with measurement of lactate dehydrogenase activity in plasma,” platelets are said to impede lactate dehydrogenase activity in plasma under conditions of low osmolality. However, their observations challenge these claims, suggesting that what appears as inhibition may actually stem from optical interference by platelets during the reaction.
Their investigation indicates that when platelet lysis is prevented and optical interference is corrected for, both platelet-rich plasma and platelet-poor plasma, as well as serum, exhibit similar levels of lactate dehydrogenase activity. Additionally, it’s worth noting that platelet contamination can lead to unexpected issues when assessing lactate dehydrogenase with centrifugal analyzers. As mentioned in the journal article, the results may vary significantly depending on the volume of diluent added with the sample, potentially causing both higher and lower readings, introducing considerable within-run fluctuations in activity.
Furthermore, platelets can scatter light during the LDH assay, leading to optical interference that affects the accuracy of the measurement. This interference can result in falsely elevated or depressed LDH levels, depending on the extent of platelet contamination and the specific assay method used. In addition, platelets contain LDH enzymes, which can contribute to the overall LDH activity measured in a plasma specimen. If platelets are not adequately removed or lysed during sample processing, their LDH activity may artificially inflate the total LDH measurement, leading to inaccurate results.
Reference: Peake MJ, Pejakovic M, Alderman MJ, Penberthy LA, Walmsley RN. Mechanism of platelet interference with measurement of lactate dehydrogenase activity in plasma. Clin Chem. 1984 Apr;30(4):518-20. PMID: 6705193.
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