EFNA1/TNFRSF1A protein level ratio in blood (OBA_2055593, an Ontology of Biological Attributes id) can be described as follows. A compound attribute that is the ratio of amount of ephrin-A1 (human) in blood to amount of tumor necrosis factor receptor superfamily member 1A (human) in blood. Also known as: the ratio of amount of ephrin-A1 (human) in blood to amount of tumor necrosis factor receptor superfamily member 1A (human) in blood.