A compound attribute that is the ratio of amount of programmed cell death 1 ligand 1 (human) in blood to amount of ephrin-A4 (human) in blood. The trait is CD274/EFNA4 protein level ratio in blood (Ontology of Biological Attributes identifier OBA_2055382). Also known as: the ratio of amount of programmed cell death 1 ligand 1 (human) in blood to amount of ephrin-A4 (human) in blood.