The nonlinearity seen for LDL-cholesterol with lyophilized material is a matrix effect.

infrequent cases of ethylene glycol poisoning. We believe that glycolic acid measurements can be useful as a supplement, but not as a substitute, to serum ethylene glycol determination, although in most cases the latter will be sufficient. Furthermore, serum ethylene glycol determined enzymatically should be confirmed by another method such as gas chromatography–mass spectrometry (6). However, in the acute setting of managing the intoxicated patient, the use of serum ethylene glycol (determined enzymatically on an automated analyzer (7, 8), anion and osmolar gaps coupled with arterial blood gases measurements will provide the greatest diagnostic yield at lowest cost. This approach is of particular utility in many medical centers that do not have access to a sophisticated reference toxicology laboratory. Thus, a recent survey of 95 teaching hospitals has shown that ethylene glycol determination was performed in only 25% of the polled hospitals (with a median turnaround time of 1.5 h), whereas if the test was sent out, the turnaround time was 42 h. (9).