Which enzyme is most useful in establishing hepatic origin of an elevated serum alkaline phosphatase?

Which enzyme is most useful in establishing hepatic origin of an elevated serum alkaline phosphatase?

• A. 5′-Nucleotidase
• B. ALANINE aminotransferase (ALT)
• C. Aspartate aminotransferase (AST)
• D. Lactate dehydrogenase

Answer: (A)

When alkaline phosphatase is elevated, you want a marker that points to liver rather than bone. 5′-Nucleotidase is more specific to the liver and its serum activity rises with hepatic or biliary sources of ALP, making it a good discriminator for hepatic origin. Bone-derived ALP does not show the same rise in 5′-nucleotidase, so a high ALP with elevated 5′-nucleotidase supports a liver source. ALT and AST indicate hepatocellular injury but don’t specifically identify the source of ALP elevation; they can be normal in some biliary problems. LDH is nonspecific and not helpful for distinguishing hepatic vs bone origins of ALP.

When alkaline phosphatase is elevated, you want a marker that points to liver rather than bone. 5′-Nucleotidase is more specific to the liver and its serum activity rises with hepatic or biliary sources of ALP, making it a good discriminator for hepatic origin. Bone-derived ALP does not show the same rise in 5′-nucleotidase, so a high ALP with elevated 5′-nucleotidase supports a liver source.

ALT and AST indicate hepatocellular injury but don’t specifically identify the source of ALP elevation; they can be normal in some biliary problems. LDH is nonspecific and not helpful for distinguishing hepatic vs bone origins of ALP.