The amount of a N-acetyllactosaminide beta-1,6-N-acetylglucosaminyl-transferase when measured in blood serum. The trait is level of N-acetyllactosaminide beta-1,6-N-acetylglucosaminyl-transferase in blood serum (OBA_2041692, an Ontology of Biological Attributes entry). Also known as: blood serum N-acetyllactosaminide beta-1,6-N-acetylglucosaminyl-transferase amount.