The amount of a glycerol-3-phosphate dehydrogenase [NAD(+)], cytoplasmic when measured in blood serum. The trait is OBA_2041770 (level of glycerol-3-phosphate dehydrogenase [NAD(+)], cytoplasmic in blood serum). Also known as: blood serum glycerol-3-phosphate dehydrogenase [NAD(+)], cytoplasmic amount.