The amount of a cyanocobalamin reductase / alkylcobalamin dealkylase when measured in blood serum. The trait is level of cyanocobalamin reductase / alkylcobalamin dealkylase in blood serum (OBA_2042384, an Ontology of Biological Attributes term). Also known as: blood serum cyanocobalamin reductase / alkylcobalamin dealkylase amount.