The amount of a bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase when measured in blood serum. The trait is level of bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase in blood serum (OBA_2041751). Also known as: blood serum bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase amount.