Breath Alcohol Analyzer Mistakes Methanol Poisoning for Alcohol Intoxication

Breath alcohol analyzers are used to detect ethanol in motorists and others suspected of public intoxication. One concern is their ability to detect interfering substances that may falsely increase the ethanol reading. A 47-year-old-man was found in a public park, acting intoxicated. A breath analyzer test (Intoxilyzer 5000EN) measured 0.288 g/210 L breath ethanol, without an interferent noted. In the emergency department, the patient admitted to drinking HEET Gas-Line antifreeze, which contains 99% methanol. Two to three hours after ingestion, serum and urine toxicology screen results were negative for ethanol and multiple other substances. His serum methanol concentration was 589 mg/dL, serum osmolality 503 mOsm/kg, osmolar gap 193 mOsm/kg, and anion gap 17 mmol/L. The patient was treated with intravenous ethanol, fomepizole, and hemodialysis without complication. This is a unique clinical case of a breath alcohol analyzer reporting methanol as ethanol. Intoxilyzer devices have been shown to indicate some substances (acetone) as interferents in humans but not methanol. Increased serum concentrations of methanol can be reported as ethanol by a commonly used breath alcohol analyzer, which can result in a delayed diagnosis or misdiagnosis and subsequent methanol toxicity if antidotal treatment is not administered in a timely manner.