The amount of a phosphatidylcholine 16:0_18:0 when measured in blood serum. The trait is level of Phosphatidylcholine (16:0_18:0) in blood serum (OBA_2045069). Also known as: blood serum phosphatidylcholine 16:0_18:0 amount, level of phosphatidylcholine 16:0_18:0 in blood serum.