Updated definitions of healthy ranges for serum alanine aminotransferase levels.

Background: Serum alanine aminotransferase (ALT) activity, the variable most commonly measured to assess hepatic disease, fails to identify many patients with hepatic injury. Current standards for "normal" ALT level were defined by using populations that included persons with subclinical liver disease.

Objective: To update definitions of healthy ranges for serum ALT level.