The amount of a Na(+)/H(+) exchange regulatory cofactor NHE-RF1 when measured in blood serum. The trait is Ontology of Biological Attributes identifier OBA_2040235 (level of Na(+)/H(+) exchange regulatory cofactor NHE-RF1 in blood serum). Also known as: blood serum Na(+)/H(+) exchange regulatory cofactor NHE-RF1 amount.