Which laboratory marker is most sensitive but nonspecific for chronic alcohol use?

• A. Bilirubin
• B. GGT
• C. AST
• D. ALT

Answer: (B)

The key idea is sensitivity versus specificity in alcohol-related markers. Gamma-glutamyl transferase (GGT) tends to rise with chronic alcohol consumption, often even when other liver tests are normal. That makes it a very sensitive indicator of alcohol use. But its elevation isn’t unique to alcohol; GGT can be increased with many other liver and biliary conditions, certain medications, diabetes, obesity, and other liver diseases. That combination—often elevated in drinkers, yet not specific to alcohol—is why it’s described as the most sensitive but nonspecific marker for chronic alcohol use.

Bilirubin reflects overall liver excretory function and can be elevated with various liver problems, but it’s not particularly sensitive to alcohol exposure. AST and ALT indicate hepatocellular injury; in alcoholic liver disease AST can be disproportionately high relative to ALT, but these enzymes aren’t as sensitive for detecting habitual alcohol use as GGT.