[Lactate Dehydrogenase - Old Tumour Marker in the Light of Current Knowledge and Preanalytic Conditions]

With the development and subsequent clinical applications of anticancer immuno-and angiomodulatory therapies and expanded knowledge on significance of tumor microenvironment for disease prognosis and treatment outcome, a classical blood analyte, lactate dehydrogenase (LDH), gains in importance as a tumor marker reflecting to some extent immunosupressive and angiogenic tumour milieu. Physical extravascular hemolysis due to complicated or inaccurate blood sampling interferes strongly with quantification of LDH in serum/plasma samples. Upon correlating circulating hemoglobin level with LDH catalytic activities in 99,937 plasma samples we quantified hemolysis interference with LDH plasma levels. An increment of LDH (μkat/l) caused by hemolysis is equal to 0.002 times circulating hemoglobin level (mg/l). Thus, hemolysis interference can be mathematically subtracted from measured LDH using a formula: [LDH (measured) (μkat/l) - 0.002 × circulating hemoglobin (mg/l) ]. In other words, each increment of hemolysis equal to 100mg/l of circulating hemoglobin will result to LDH increase equal to 0.2 μkat/l. As one of the emerging predictors of treatment outcome, a cancer prognostic biomarker and dynamic tumor marker, serum/plasma LDH concentration needs to be interpreted with respect to reported hemolysis level. Also, for these purposes, quantitative determination of serum/plasma levels of free circulating hemoglobin has to be routinely performed.Key words: lactate dehydrogenase - hemolysis - preanalytical error This work was supported by MEYS via NPS I for RECAMO2020 (LO1413). The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 13. 3. 2017Accepted: 26. 3. 2017.