The amount of a Phosphatidylcholine (O-16:1_18:0) when measured in blood serum. The trait is Ontology of Biological Attributes term OBA_2045119 (level of Phosphatidylcholine (O-16:1_18:0) in blood serum). Also known as: blood serum Phosphatidylcholine (O-16:1_18:0) amount.