The amount of a succinyl-CoA:3-ketoacid-coenzyme A transferase 1, mitochondrial when measured in blood serum. The trait is level of succinyl-CoA:3-ketoacid-coenzyme A transferase 1, mitochondrial in blood serum (OBA_2042726, an Ontology of Biological Attributes entry). Also known as: blood serum succinyl-CoA:3-ketoacid-coenzyme A transferase 1, mitochondrial amount.