The amount of a Kazal-type serine protease inhibitor domain-containing protein 1 (human) when measured in blood. The trait is amount of Kazal-type serine protease inhibitor domain-containing protein 1 (human) in blood (Ontology of Biological Attributes entry OBA_2052625). Also known as: blood Kazal-type serine protease inhibitor domain-containing protein 1 (human) amount.