GFRA1/SPON2 protein level ratio in blood (Ontology of Biological Attributes identifier OBA_2053698) can be described as follows. A compound attribute that is the ratio of amount of GDNF family receptor alpha-1 (human) in blood to amount of spondin-2 (human) in blood. Also known as: the ratio of amount of GDNF family receptor alpha-1 (human) in blood to amount of spondin-2 (human) in blood.