The amount of a polypeptide N-acetylgalactosaminyltransferase 2 when measured in blood serum. The trait is level of polypeptide N-acetylgalactosaminyltransferase 2 in blood serum (OBA_2041664, an Ontology of Biological Attributes term). Also known as: blood serum polypeptide N-acetylgalactosaminyltransferase 2 amount.