Accuracy of point-of-care measurements
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* Philippe G. Jorens, MD PhD

*   © 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.

## Footnotes

*   **Competing interests:** None declared.

## REFERENCES

1.  1. Brindley PG, Butler MS, Cembrowski G, et al. Falsely elevated point-of-care lactate measurement after ingestion of ethylene glycol. CMAJ 2007;176:1097-9.
    
    [Abstract/FREE Full Text](http://www.cmaj.ca/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoiY21haiI7czo1OiJyZXNpZCI7czoxMDoiMTc2LzgvMTA5NyI7czo0OiJhdG9tIjtzOjIxOiIvY21hai8xNzcvOS8xMDcwLmF0b20iO31zOjg6ImZyYWdtZW50IjtzOjA6IiI7fQ==) 

2.  2. Jorens PG, Demey HE, Schepens PJC, et al. Unusual D-lactic acid acidosis from propylene glycol metabolism in overdose. J Toxicol Clin Toxicol 2004;42:163-9.
    
    [PubMed](http://www.cmaj.ca/lookup/external-ref?access_num=15214621&link_type=MED&atom=%2Fcmaj%2F177%2F9%2F1070.atom) 
    
    [Web of Science](http://www.cmaj.ca/lookup/external-ref?access_num=000222009700006&link_type=ISI)