The amount of a hydroxymethylglutaryl-CoA synthase, cytoplasmic when measured in blood serum. The trait is Ontology of Biological Attributes id OBA_2041892 (level of hydroxymethylglutaryl-CoA synthase, cytoplasmic in blood serum). Also known as: blood serum hydroxymethylglutaryl-CoA synthase, cytoplasmic amount.