The amount of a phosphatidylinositol 16:0_18:1 when measured in blood serum. The trait is Ontology of Biological Attributes term OBA_2045152 (level of Phosphatidylinositol (16:0_18:1) in blood serum). Also known as: blood serum phosphatidylinositol 16:0_18:1 amount, level of phosphatidylinositol 16:0_18:1 in blood serum.