CA3/HMBS protein level ratio in blood (OBA_2054816, an Ontology of Biological Attributes identifier) can be described as follows. A compound attribute that is the ratio of amount of carbonic anhydrase 3 (human) in blood to amount of porphobilinogen deaminase (human) in blood. Also known as: the ratio of amount of carbonic anhydrase 3 (human) in blood to amount of porphobilinogen deaminase (human) in blood.