A compound attribute that is the ratio of amount of carbonic anhydrase 1 (human) in blood to amount of carbonic anhydrase 3 (human) in blood. The trait is CA1/CA3 protein level ratio in blood (Ontology of Biological Attributes identifier OBA_2055730). Also known as: the ratio of amount of carbonic anhydrase 1 (human) in blood to amount of carbonic anhydrase 3 (human) in blood.