Laboratory investigations

None of the tests mentioned below may be positive in heavy drinkers. However, all the tests described may be positive in other conditions and are not pathognomonic for alcoholism.

• gamma-glutamyl-transferase (normal value less than 40 i.u. per litre) - the levels of this enzyme are raised in about 80% of problem drinkers. The level of increase in levels of this enzyme are in relation to heaviness of drinking.
• mean corpuscular volume (MCV) - this value is raised in over half of patients with alcohol dependence. It is more commonly raised in women with alcohol dependence than men. The value of MCV will return to normal if there is abstinence for several weeks. Normal is 80 to 90 fl.
• abnormal ALT reflects hepatocellular damage. If the AST:ALT ratio is greater than 2 then this is suggestive of alcohol damage.
• blood alcohol concentration - raised as a result of an isolated drinking episode and chronic abuse. However an individual who has a blood alcohol level above 80mg per 100 ml - the legal limit for driving - and is not intoxicated is likely to be a chronic heavy drinker. Greater than 150mg per 100ml is practically diagnostic if measured under particular circumstances, for example in clinic. Unconsciousness occurs at levels over 300mg per 100ml.
• creatinine phosphokinase (normal less than 150 i.u. per litre) - raised in 50% of problem drinkers
• urate and fasting triglycerides raised in 50% of problem drinkers.