Quantification of the amount of 1-(1-enyl-stearoyl)-2-docosahexaenoyl-GPC (P-18:0/22:6) in a sample. The trait is Experimental Factor Ontology entry EFO_0800424 (1-(1-enyl-stearoyl)-2-docosahexaenoyl-GPC (P-18:0/22:6) measurement).