Assessing the Role of Initial Serum Calcium Concentration in Patients with Ethylene Glycol Poisoning

Assays for ethylene glycol (EG) with a rapid turn-around time are not routinely available. Clinicians must rely on historical features and readily available clinical tests, combined with clinical acumen, to guide the initial management of suspected EG poisoning. Hypocalcemia has been suggested as a clue supporting the diagnosis of EG poisoning in patients presenting with an unexplained high anion gap metabolic acidosis (HAGMA). A previous small study challenged this assumption.

This was a retrospective case series of one state's poison control system of confirmed EG-poisoned patients between September 2017 and April 2021. The definition of EG poisoning was based on suspected EG ingestion and a serum EG concentration > 5 mg/dL. Patients who were suspected to have EG toxicity but did not have a confirmed EG concentration or the EG concentration was less than 5 mg/dL were excluded. Routine laboratory studies were recorded for all patients. Comparisons between serum calcium on presentation to presenting blood pH, bicarbonate, anion gap, and creatinine were assessed for correlation.

There was no correlation between the presenting calcium and either pH or creatinine. There was a weak positive correlation between the initial serum calcium and anion gap, a weak negative correlation between the initial serum calcium and bicarbonate.

On hospital presentation, hypocalcemia was not associated with EG poisoning, even in patients with a HAGMA. A normal serum calcium on presentation does not exclude the diagnosis of EG poisoning.