Now that routine laboratory testing is automated and is frequently part of an annual checkup, physicians are often faced with the problem of a patient with one abnormal result on measurement of serum aminotransferases or alkaline phosphatase but no symptoms. Many batteries of screening tests now include measurement of serum alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and γ-glutamyltransferase. Although these enzymes are present in tissues throughout the body, they are most often elevated in patients with liver disease and may reflect liver injury.

The first step in the evaluation of a patient with elevated liver-enzyme levels but no symptoms is . . .