The amount of a CMP-N-acetylneuraminate-poly-alpha-2,8-sialyltransferase when measured in blood serum. The trait is Ontology of Biological Attributes id OBA_2043684 (level of CMP-N-acetylneuraminate-poly-alpha-2,8-sialyltransferase in blood serum). Also known as: blood serum CMP-N-acetylneuraminate-poly-alpha-2,8-sialyltransferase amount.