The amount of a Phosphatidylcholine (O-18:0_14:0) when measured in blood serum. The trait is level of Phosphatidylcholine (O-18:0_14:0) in blood serum (OBA_2045125, an Ontology of Biological Attributes identifier). Also known as: blood serum Phosphatidylcholine (O-18:0_14:0) amount.