This assay is used for the in vitro quantitative determination of Active-B12 (holotranscobalamin) in human serum and plasma, aiding in the assessment of vitamin B12 deficiency. Active-B12 is the biologically available form of cobalamin bound to transcobalamin, which is taken up by cells via specific receptors. Unlike the larger, inactive fraction bound to haptocorrin, Active-B12 reflects the functional B12 status more accurately and serves as an early indicator of deficiency. Clinically, it helps diagnose conditions like megaloblastic anemia caused by vitamin B12 deficiency. Common testing methods include ELISA, chemiluminescence, and immunofluorescence.
