As many of the clinical signs and symptoms of ethylene glycol poisoning are nonspecific and occur in many poisonings the diagnosis is often difficult.[24] It is most reliably diagnosed by the measurement of the blood ethylene glycol concentration. Ethylene glycol in biological fluids can be determined by gas chromatography.[25] Many hospital laboratories do not have the ability to perform this blood test and in the absence of this test the diagnosis must be made based on the clinical presentation of the patient.[7] In this situation a helpful test to diagnose poisoning is the measurement of the osmolal gap. The patients' serum osmolality is measured by freezing point depression and then compared with the predicted osmolality based on the patients' measured sodium, glucose, blood urea nitrogen, and any ethanol that may have been ingested. The presence of a large osmolal gap supports a diagnosis of ethylene glycol poisoning. However, a normal osmolar gap does not rule out ethylene glycol exposure because of wide individual variability.[26][27]
The increased osmolal gap is caused by the ethylene glycol itself. As the metabolism of ethylene glycol progresses there will be less ethylene glycol and this will decrease the blood ethylene glycol concentration and the osmolal gap making this test less useful.[28] Additionally, the presence of other alcohols such as ethanol, isopropanol, or methanol or conditions such as alcoholic or diabetic ketoacidosis, lactic acidosis, or kidney failure may also produce an elevated osmolal gap leading to a false diagnosis.[7]
Other laboratory abnormalities may suggest poisoning, especially the presence of a metabolic acidosis, particularly if it is characterized by a large anion gap. Large anion gap acidosis is usually present during the initial stage of poisoning. However, acidosis has a large number of differential diagnosis, including poisoning from methanol, salicylates, iron, isoniazid, paracetamol, theophylline, or from conditions such as uremia or diabetic and alcoholic ketoacidosis. The diagnosis of ethylene glycol poisoning should be considered in any patient with a severe acidosis.[7] Urine microscopy can reveal needle or envelope-shaped calcium oxalate crystals in the urine which can suggest poisoning; although these crystals may not be present until the late stages of poisoning.[29] Finally, many commercial radiator antifreeze products have fluorescein added to enable radiator leaks to be detected using a Wood's lamp. Following ingestion of antifreeze products containing ethylene glycol and fluorescein, a Wood's lamp may reveal fluorescence of a patient’s mouth area, clothing, vomitus, or urine which can help to diagnose poisoning.[30][31]
Signs of ethylene glycol poisoning depend upon the time after ingestion.[6] Symptoms usually follow a three-step progression, although poisoned individuals will not always develop each stage.[7][8]
Stage 1 (30 minutes to 12 hours) consists of neurological and gastrointestinal symptoms and looks similar to alcohol poisoning.[9] Poisoned individuals may appear to be intoxicated, dizzy, lacking coordination of muscle movements, drooling, depressed,[6] and have slurred speech, seizuring, abnormal eye movements, headaches, and confusion.[9] Irritation to the stomach may cause nausea and vomiting.[7] Also seen are excessive thirst and urination.[9] Over time, the body metabolizes ethylene glycol into other toxins.&Stage 2 (12 to 36 hours) where signs of "alcohol" poisoning appear to resolve, underlying severe internal damage is still occurring.[9] An elevated heart rate, hyperventilation or increased breathing effort, and dehydration may start to develop, along with high blood pressure and metabolic acidosis.[9] These symptoms are a result of accumulation of organic acids formed by the metabolism of ethylene glycol. Additionally low calcium concentrations in the blood, overactive muscle reflexes, muscle spasms, QT interval prolongation, and congestive heart failure may occur. If untreated, death most commonly occurs during this period.[7]&Stage 3 (24 to 72 hours) kidney failure is the result of ethylene glycol poisoning. In cats, this stage occurs 12–24 hours after getting into antifreeze; in dogs, at 36–72 hours after getting into antifreeze.[9] During this stage, severe kidney failure is developing secondary to calcium oxalate crystals forming in the kidneys.[9] Severe lethargy, coma, depression, vomiting, seizures, drooling, and inappetance may be seen.[9] Other symptoms include acute tubular necrosis, red blood cells in the urine, excess proteins in the urine, lower back pain, decreased or absent production of urine, elevated blood concentration of potassium, and acute kidney failure.[10][11] If kidney failure occurs it is typically reversible, although weeks or months of supportive care including hemodialysis may be required before kidney function returns.[7