For ALL Ethylene Glycol tests, please notify LabLINK on extension 22000 before sending to LabPLUS.
There are only limited data available for using plasma/serum ethylene glycol concentrations as a guide to diagnosis and treatment of acute ethylene glycol poisoning. The information regarding indication and cut points for treatment quoted below are for reference only.
NOTE: Management guidance including criteria for starting an antidote (ethanol/fomepizole) in poisoning with ethylene glycol, or methanol has been updated in 2023. Clinicians should discuss with a toxicologist. The New Zealand (NZ) National Poison Centre phone number is 0800 764 766, or website http://toxinz.com
In Te Toka Tumai (Auckland District), consult local ED experts and refer to management guidance on intranet.
Glycolic acid spot test
In acute ethylene glycol poisoning, glycolic acid is the main toxic metabolite which causes metabolic acidosis and organ damage.
If ethylene glycol poisoning is suspected, at LabPlus, the glycolic acid spot test is available 24hrly as a qualitative screening test. It can be performed within short notice and a result is usually available in around 1-2 hours.
NOTE: If the patient presents very early or if there is concurrent ingestion of ethanol or treatment by ethanol/fomepizole then a negative glycolic acid spot test result does not exclude ethylene glycol poisoning. As a toxic metabolite of ethylene glycol, there is a lag phase for glycolic acid to appear in circulation, especially if ethanol is also present (which retards the metabolism of ethylene glycol). The glycolic acid spot test also cannot reliably be used to determine when to stop ethanol/fomepizole or haemodialysis treatment.
Ethylene glycol / glycolic acid quantification by GC-MS (Gas chromatography mass spectrometry)
The ethylene glycol / glycolic acid quantification test measures both ethylene glycol and glycolic acid in the blood. It is generally not available outside normal working hours as it involves complex analytical procedures. It is usually performed retrospectively as a confirmation of a positive spot test finding, based on clinical needs.
The serum glycolic acid concentration (measured simultaneously with ethylene glycol) and plasma bicarbonate concentration correlates better with clinical toxicity than the ethylene glycol concentration. As a very rough guide, serum glycolic acid > 10 mmol/L (76 mg/dL) corresponds to bicarbonate of < 20 mmol/L and a blood pH of < 7.25.
|
General guidelines for treatment (updated 2023) - NOTE: Specific cases should be discussed with a toxicologist
Fomepizole is indicated if:
Either: Patient has a serum ethylene glycol concentration >3.2 mmol/L
OR
Either: Patient has a documented recent history of ethylene glycol ingestion with increased osmolal gap of >10mOsm/L
(Note: Osmolal gap = measured serum osmolarity (mOsm/kg, measured by freezing point depression in the lab) minus calculated osmolality = 2x [Na+] + [glucose] + [urea] + ethanol (if present) (all in mmol/L)
OR
Both: Patient has a history of ethylene glycol ingestion; AND at least two of the following:
- Arterial pH <7.3; or
- Serum bicarbonate <20 mmol/L; or
- Osmolal gap >10mOsm/L; or
- Urinary oxalate crystals present (only in ethylene glycol poisoning cases)
Treatment end point is when the patient's ethylene glycol concentration is <3.2 mmol/L, symptoms have resolved AND pH has normalised.
Antidote treatment should not be withheld while awaiting either the glycolic acid spot test or ethylene glycol quantitation
If ethanol is used, the aim is to maintain serum ethanol concentrations between 22 - 33 mmol/L.
Indications for Haemodialysis:
1. Ethylene glycol concentration > 8 mmol/L (50 mg/dL), or
2. Any ethylene glycol concentration in the presence of severe, unresponsive metabolic acidosis, acute renal failure, severe electrolyte imbalance, or deteriorating condition despite supportive measures.
Consider initiation of haemodialysis of the glycolic acid concentration is >8 mmol/L (61 mg/dL).
Provided the metabolism of ethylene glycol to glycolic acid is adequately and stably inhibited by an antidote such as ethanol, a serum glycolic acid of < 8 mmol/L (61 mg/dL) probably does not require haemodialysis, regardless of the ethylene glycol concentration.
Consider stopping haemodialysis if the ethylene glycol concentration is <0.8 mmol/L (5 mg/dL), or
If the ethylene glycol concentration is <3.2 mmol/L (20 mg/dL) and the acid base abnormalities and signs of systemic toxicity disappear.
NOTE: Possible false lactate elevation on point of care instruments due to glycolic acid
Ethylene glycol poisoning can be associated with raised lactate, however glycolic acid can also cause false lactate elevation, especially on point of care (POCT) instruments, due to the glycolic acid cross-reacting as a substrate for the lactate oxidase method used. The interference is usually much less, but not entirely absent on lactate measurements using main laboratory analysers. Finding a "lactate gap", the difference between POCT and laboratory lactate results, can sometimes be a clue to the presence of glycolate.
References:
1. Beaulieu J, et al. Treating ethylene glycol poisoning with alcohol dehydrogenase inhibition, but without extracorporeal treatments: a systematic review. Clin. Toxicol. 2022. https://www.tandfonline.com/doi/full/10.1080/15563650.2022.2049810
2. Antidotes for poisoning by alcohols that form toxic metabolites. Br.J.Clinical Pharmacol.. 2015. 81:2;505-15.
3. N. Engl. J. Med. 2018; 378:270-80
4. Lim, J et al. Ethylene glycol poisoning: mind the gap. NZMJ 17 May 2019; Vol 132 No 1495. ISSN 1175-8716.
Uncertainty of Measurement:
Ethylene Glycol 12%
Glycolic acid 26%
Conversion factors:
Ethylene glycol: mg/dL = mmol/L x 6.2
Glycolic acid: mg/dL = mmol/L x 7.6
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427
For ALL Ethylene Glycol tests, please notify LabLINK on extension 22000 before sending to LabPLUS.
A minimum of 0.5mL serum or plasma (heparin or EDTA) is required for this screen test.
Separate and aliquot before sending.
An additional 0.2mL serum or plasma is required if further testing is necessary.
Send at 2-8 degrees.