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"Hemolysis"--toward clearer terminology.

To the Editor.--In their recent article on correction factors for estimating potassium concentrations in samples with in vitro hemolysis, Mansour et al (1) argue strongly against the practice of using correction factors to estimate potassium concentrations in samples with in vitro hemolysis. They provide an excellent description of the various experimental models used and the range of published correction factors as evidence of the complexity in this area.

One source of confusion in studies on this topic has been the differing use of the word hemolysis. Hemolysis comes from the Latin hemo (blood) and lysis (to break open). The medical subject heading definition of hemolysis used by the National Library of Medicine is "destruction of erythrocytes...." (2) Some authors have restricted its use to red cells only (erythrolysis) while others have used it to cover all blood cells (pancytolysis). (3,4) There is similar variation in its use to describe lysis alone or to include any damage or leakage from blood cells, intact or lysed. (4,5) As described by Mansour et al, nonlytic changes in blood cell integrity, such as shear-induced deformation damage and membrane permeability changes, are potentially important sources of potassium leakage in the preanalytical phase. However, they will not be mirrored in the free hemoglobin concentration (and hemolysis index measurement), which will necessarily reflect only red cell lysis. Higher and more variable correction factors from mechanical trauma models (which include cellular integrity changes) would be expected compared with lysis models and this is supported by the authors' summary of the published data. The approaches used by Mansour et al include nonlytic cellular integrity changes in addition to lysis and therefore deliver correction factors closer to the mechanical trauma models than the lysis ones. Their second approach of database mining is a particularly strong one and better reflects the full spectrum of preanalytical sample integrity changes seen in practice, making no assumptions about mechanism or frequency. However, the generalizability of database-generated correction factor estimates may be limited by local preanalytical (collection and transport) and patient population (disease and age) conditions. Distinction between lysis and other nonlytic cellular integrity changes is important in the case of potassium but may be less relevant for other analytes depending on molecular size, physiology, and the mechanisms of interference. The appropriateness of the use of lysis models in analytical interference studies should thus be decided on an analyte-by-analyte basis. More specific use of terminology to differentiate lysis of different cell types (erythrolysis, leukolysis, thrombocytolysis, pancytolysis) and mechanisms of cell damage (lysis, leakage) is needed to clarify discussions on this topic.

Robert Hawkins, MB, ChB, FRCPA

Department of Laboratory Medicine

Tan Tock Seng Hospital

11 Jalan Tan Tock Seng, Singapore 308433

(1.) Mansour MM, Azzazy HM, Kazmierczak SC. Correction factors for estimating potassium concentrations in samples with in vitro hemolysis: a detriment to patient safety. Arch Pathol Lab Med. 2009;133(6):960-966.

(2.) National Library of Medicine. Search MeSH for "hemolysis." Accessed January 10, 2010.

(3.) Lippi G, Blanckaert N, Bonini P, et al. Haemolysis: an overview of the leading cause of unsuitable specimens in clinical laboratories. Clin Chem Lab Med. 2008;46(6):764-772.

(4.) Dimeski G, Clague AE, Hickman PE. Correction and reporting of potassium results in haemolysed samples. Ann Clin Biochem. 2005;42(pt 2): 119-123.

(5.) Hawkins R. Variability in potassium/hemoglobin ratios for hemolysis correction. Clin Chem. 2002;48(5):796.

The author has no relevant financial interest in the products or companies described in this article.
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Title Annotation:Letters to the Editor
Author:Hawkins, Robert
Publication:Archives of Pathology & Laboratory Medicine
Article Type:Letter to the editor
Date:Aug 1, 2010
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