Methanol, Serum

Specimen requirement	Adult patient: Clotted blood tube (Clot activator tube) Minimum blood volume: 6 mL
Specimen requirement	Paediatric patient: Paediatric clotted blood tube Number of vials: 2 Minimum blood volume: 1.6 mL
Authorisation code required	Yes
24 Hr available service	Yes
Method	Screening by colourimetric method Confirmation by Gas Chromatography-Flame Ionisation Detection (GC-FID)
Reference interval	Normally not detected.
Clinical indication	Detection of ingestion of methanol
Result interpretation	Methanol poisonings are usually due to accidental ingestion by children or by alcoholics, or self-poisoned in attempted suicide. Accumulation of methanol metabolites causes metabolic acidosis, optic nerve damage and necrosis of pancreas. Prompt treatment with high dose of ethanol is life-saving and may preserve the eyesight. Methanol (wood alcohol) is a common ingredient in many solvents, windshield-washing solutions, duplicating fluids and paint removers. It is sometimes used as an ethanol substitute by alcoholics. Although methanol itself produces mainly inebriation, its metabolic products may cause metabolic acidosis, blindness, and death after a characteristic latent period of 6 - 30 Hr. Methanol is slowly metabolised by alcohol dehydrogenase to formaldehyde and subsequently by aldehyde dehydrogenase to formic acid (formate). Systemic acidosis is caused by the formic acid as well as by lactic acid, while blindness is caused primarily by formate. Both ethanol and methanol compete for the enzyme alcoholic dehydrogenase; the preference of this enzyme for metabolising ethanol forms the basis for ethanol therapy in methanol poisonings. The fatal oral dose of methanol is estimated to be 30 - 240 mL (20 - 150) g. The minimum toxic dose is approximately 100 mg/Kg. Elevated serum methanol levels have been reported after extensive dermal exposure and concentrated inhalation. Serum methanol levels higher than 20 mg/dL (6.23 mmol/L) are considered to be toxic. While levels higher than 40 mg/dL (12.47 mmol/L) is considered to be very serious, rapid removal of both methanol and formate by haemodialysis is indicated. After the latent period, a low or non-detectable methanol level does not rule out serious intoxication in a symptomatic patient because all the methanol may already have been metabolised to formate.
Measurement of uncertainty	N. A.
Frequency of measurement	Urgent for methanol screening test Specimen positive in methanol screening test will be proceeded for methanol quantitation test on the next working day.