The amount of a serine/threonine-protein kinase/endoribonuclease IRE1 when measured in blood serum. The trait is level of serine/threonine-protein kinase/endoribonuclease IRE1 in blood serum (OBA_2041507, an Ontology of Biological Attributes identifier). Also known as: blood serum serine/threonine-protein kinase/endoribonuclease IRE1 amount.