The amount of a (4E,8E,10E-d18:3)sphingosine when measured in blood serum. The trait is level of (4E,8E,10E-d18:3)sphingosine in blood serum (Ontology of Biological Attributes entry OBA_2045044). Also known as: blood serum (4E,8E,10E-d18:3)sphingosine amount.