Elevated levels of serum enzymes are frequently associated not only with alcohol-
related organ damage but also with excessive alcohol consumption and alcoholism without
significant tissue injury. However, both in the early detection of alcoholism as well as
also in the diagnosis of alcohol-related diseases the sensitivities and specificities of these
enzyme markers vary considerably. They may be influenced by nonalcohol-related diseases,
enzyme-inducing drugs, nutritional factors, metabolic disorders, age, smoking, etc. Consequently,
we have neither a single laboratory test - enzyme marker - nor a test combination
that is reliable enough for the exact diagnosis between alcohol- and nonalcohol-related organ
damage.
In most cases it is possible to determine the tissue from which the elevated enzyme is
derived, but only occasionally enzyme changes reflect the quantity of the tissue injury.
Gamma-glutamyltransferase (GGT) is the most widely used laboratory marker of alcoholism
and heavy drinking, detecting 34-85% of problem drinkers and alcoholics. However, the
unspecificity of increased serum GGT limits its use for general screening purposes. Its value
in the follow-up of various treatment programs, however, is well established.
An elevated level of serum aspartate aminotransferase (ASAT) and alanine aminotransferase
(ALAT) in an alcoholic or a heavy consumer indicates alcohol-induced organ damage.
The use of test combinations significantly improves the information received with single
serum enzyme determinations. An ASAT/ALAT ratio greater than 1.5 can be considered as
highly suggestive for the alcoholic etiology of the liver injury. Still better discrimination
between alcoholic and nonalcoholic origin of the liver disease may be achieved by the determination
of the ratio of GGT to alkaline phosphatase. If this ratio exceeds 1.4 the specificity
of the finding in favor for alcoholic liver injury is 78%.