A compound attribute that is the ratio of amount of collagen alpha-1(XVIII) chain (human) in blood to amount of retinoic acid receptor responder protein 2 (human) in blood. The trait is Ontology of Biological Attributes identifier OBA_2053868 (COL18A1/RARRES2 protein level ratio in blood). Also known as: the ratio of amount of collagen alpha-1(XVIII) chain (human) in blood to amount of retinoic acid receptor responder protein 2 (human) in blood.