The amount of a PI(16:0_20:4) when measured in blood serum. The trait is Ontology of Biological Attributes entry OBA_2045154 (level of Phosphatidylinositol (16:0_20:4) in blood serum). Also known as: blood serum PI(16:0_20:4) amount, level of PI(16:0_20:4) in blood serum.