- © 2007 Canadian Medical Association or its licensors
In a helpful case report in CMAJ, Peter Brindley and colleagues reported falsely elevated lactate levels obtained with a point-of-care analyzer and low plasma lactate levels obtained with laboratory testing in a patient who had ingested ethylene glycol.1 Further investigation showed that the addition of even small amounts of glycolic acid or glyoxylic acid (the 2 predominant metabolites of ethylene glycol) to blood analyzed in the Radiometer ABL 700 point-of-care analyzer resulted in a marked artifactual elevation in lactate levels. Such elevations were not seen with the other analyzers tested (including the Vitros laboratory analyzer).
We recently reported a comparable observation in a man who accidentally ingested a large amount of propylene glycol.2 Arterial blood gas analysis with the Radiometer ABL 700 point-of-care analyzer showed a very high concentration of lactate (up to 39 mmol/L), but a normal reading was obtained with the Vitros laboratory analyzer. However, in our case the falsely elevated reading with the point-of-care analyzer was not caused by any interference with propylene glycol or its metabolites. Analysis with a sensitive and specific D-lactate kit revealed the presence of a very high amount (more than 100 mmol/L) of D-lactate but not L-lactate. Interference in this case was apparently due to the intestinal conversion of the orally ingested propylene glycol into D-lactate, which was erroneously measured as L-lactate by the point-of-care analyzer.
The key objective of point-of-care testing is to generate a result quickly so that appropriate treatment can be implemented, leading to an improved clinical or economic outcome. These 2 cases show that it is crucial, especially in patients intoxicated with glycols, to confirm extreme point-of-care results with laboratory testing.
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Competing interests: None declared.