The amount of a methionine-R-sulfoxide reductase B3, mitochondrial when measured in blood serum. The trait is level of methionine-R-sulfoxide reductase B3, mitochondrial in blood serum (OBA_2042444, an Ontology of Biological Attributes id). Also known as: blood serum methionine-R-sulfoxide reductase B3, mitochondrial amount.