Preliminary evaluation of a quantitative ethylene glycol test in dogs and cats
Nancy Collicutt, DVM, MS, Dipl. ACVP
Antech Diagnostics
Smyrna, Georgia
Sharon Bush, MT (ASCP)
College of Veterinary Medicine
University of Georgia
501 D.W. Brooks Drive
Athens, Georgia
Ethylene glycol (EG) toxicity is commonly encountered in dogs and cats. Ethylene glycol is
most commonly found in automotive antifreeze and is also used as a precursor to industrial
polymers. It is a colorless, odorless, and sweet-tasting solution. After ingestion, the solution is
rapidly absorbed and reaches peak serum concentrations within 4 hr and has a half-life of 3 hr in
human beings. In dogs, the peak serum concentration is reached after 2 hr and the half-life is 3.4
hr. The published minimum lethal dose in cats is 1.4 ml/kg and in dogs is 4.4–6.6 ml/kg of body
weight; death is usually a result of acute renal failure. Mortality after ingestion of EG is 96–
100% in cats and 59–70% in dogs.
To date, there is only 1 semiquantitative point-of-care EG test available to the veterinary market
(Kacey ethylene glycol test, Kacey Inc., Asheville, NC). The test requires 20 µl of plasma and is
reported to detect levels of EG as low as 20 mg/dl (the feline lethal serum concentration).
Unfortunately, at the time of publication, there is no published data to support this claim, and a
previous study suggests that the accuracy of this test is poor. Another point-of-care qualitative
test EGT test kit (Allelic Biosystems, Kearneysville, WV) is advertised to accurately detect EG
levels above 50 mg/dl (the canine lethal serum concentration), which is above the lethal serum
concentration in cats. Gas chromatography–mass spectroscopy (GC-MS) is considered to be the
gold standard to detect serum or plasma levels of EG in human and veterinary patients, but this
test is not a cage-side test, which may result in delays in diagnosis and initiation of therapy. A
urine fluorescence test for sodium fluorescein, a common additive to some commercially
available antifreeze solutions, may aid in the rapid detection of an antifreeze exposure, but this
compound may be undetectable greater than 4–6 hours after ingestion and may cause falsenegative results. Also, administration of other drugs such as benzodiazepines may cause falsepositive results due to the florescence of their urine metabolites. Due to lack of available pointof-care testing, the decision to treat may be entirely based on clinical history of ingestion of EG
or clinicopathologic data suggestive of intoxication (increased anion gap or hyperosmolarity).
The Catachem EG reagent was developed in response to the perceived need for a rapid
quantitative test to replace the more cumbersome GC-MS methodologies. The test was designed
to measure serum or plasma EG levels using existing clinical chemistry analyzers (Hitachi Pmodular 800, Roche Diagnostics, Indianapolis, IN). The test utilizes a bacterial-sourced glycerol
dehydrogenase enzyme to catalyze an oxidation-reduction reaction of EG in the presence of
nicotinamide adenine dinucleotide (NAD +). NADH produced by this reaction is then detected at
a 340 nm wavelength where the absorption signal is proportional to the concentration of EG in
the sample. To eliminate propylene glycol and glycerol interference, the test is programmed into
the analyzer in such a way that measurement readings for EG do not begin until after any
Preliminary evaluation of a quantitative ethylene glycol test in dogs and cats
Nancy Collicutt, DVM, MS, Dipl. ACVP
Antech Diagnostics
Smyrna, Georgia
Sharon Bush, MT (ASCP)
College of Veterinary Medicine
University of Georgia
501 D.W. Brooks Drive
Athens, Georgia
endogenous glycerol or propylene glycol has been consumed by glycerol dehydrogenase. The
chemistry is then run as a two-point kinetic test with the absorbance difference between the first
and second read points being directly proportional to the level of EG in the sample.
The purpose of the current study was to determine if the Catachem EG kit (Catachem Inc.,
Oxford, CT) would quantitatively determine the amount of EG present in canine and feline
serum and plasma with in vitro addition of EG. It was hypothesized that the Catachem EG kit
would precisely and accurately detect the presence of EG at various concentrations associated
with toxicity in companion animals.
Serum and plasma samples were spiked at various concentrations of EG (0, 20, 60, and 100
mg/dl) and analyzed using the Catachem kit. Twenty randomly selected samples were also
submitted for gas chromatography–mass spectroscopy (GC-MS) analysis of EG concentration,
which was considered the gold standard. Inter- and intra-assay coefficients of variation (CVs)
were calculated. Bland–Altman analysis was performed to compare the Catachem results to the
GC-MS analyses. Analysis of serum samples showed a bias of 8.48 mg/dl (95% limits of
agreement: 17.8 to −0.9 mg/dl) while spiked plasma samples had a bias of 7.32 mg/dl (18.1 to
−3.5 mg/dl). Intra-assay CV was 0.7%. Interassay CV ranged from 1.2% to 2.0%. For all
samples, the Catachem kit read higher than GC-MS values and slightly overestimated in vitro
concentrations.
The Catachem test kit is an accurate quantitative test for EG in dogs and cats that may aid in
timely recognition of EG exposure. Because of the positive bias in all samples, some pets may
receive treatment unnecessarily. However, animals with blood EG concentrations at or above the
published lethal serum or plasma concentration will be readily identified so that treatment may
be initiated.
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Preliminary evaluation of a quantitative ethylene glycol test in dogs and cats
Nancy Collicutt, DVM, MS, Dipl. ACVP
Antech Diagnostics
Smyrna, Georgia
Sharon Bush, MT (ASCP)
College of Veterinary Medicine
University of Georgia
501 D.W. Brooks Drive
Athens, Georgia
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