Obesity as a cause of "false-positive" alcohol misuse laboratory investigations.

Three patients are reported with a prior history of alcohol misuse accompanied by abnormal liver toxicity tests and other indices of alcohol misuse. A decreased but persistently raised serum gamma-glutamyl transferase activity during subsequent abstinence or controlled drinking was interpreted incorrectly as due to continued alcohol misuse whereas obesity-related fatty liver was the probable cause. The value of serum carbohydrate deficient transferrin assays in the differential diagnosis of abnormal liver toxicity tests is emphasized.