The amount of a leukocyte immunoglobulin-like receptor subfamily A member 3 when measured in blood serum. The trait is level of leukocyte immunoglobulin-like receptor subfamily A member 3 in blood serum (Ontology of Biological Attributes term OBA_2042196). Also known as: blood serum leukocyte immunoglobulin-like receptor subfamily A member 3 amount.