Specimen Collection
Plain4.5 mL Plain Serum (Always Required)
Minimum volume of serum 500uL
Microsample 0.5 mL Paediatric Microsample Blood (Always Required)
SST4.5 mL Adult SST Blood
Micro-SST0.5 mL Paediatric Micro-SST Blood
Reference Intervals
The reference interval will be provided with the result
Diagnostic Use and Interpretation
The major fraction (80%) of plasma B12 is bound to haptocorrin (transcobalamin I). This fraction is unavailable to cells, and appears to be inactive.
The active B12 fraction (20%) is bound to transcobalamin II. The complex of B12 bound to transcobalamin II is called holotranscobalamin or active B12.
Some patients have transcobalamin I deficiency, resulting in low plasma total B12 levels with normal active B12 levels. These patients are not B12 deficient.
Patients with Transcobalamin II deficiency or with inborn errors of cobalamin biosynthesis resulting in combined deficiency of both adenosylcobalamin and methylcobalamin also have methylmalonic aciduria (cblC, cblD or cblF disease), and homocystinuria and hyperhomocysteinaemia.
Transcobalamin II deficiency may cause megaloblastic anaemia in addition to CNS dysfunction.
References
Carmel, R. (2003). "Mild transcobalamin I (haptocorrin) deficiency and low serum cobalamin concentrations." Clin Chem 49 (8): 1367-1374.
Laboratory Notes
Any queries please contact Section Leader/Technical Specialist SCP - Special Techniques
Plain tube only
Not performed at LabPlus. Serum specimens are sent to Canterbury Health Laboratories for analysis - not urgent.
Check two points of ID are on the aliquot tube. Store and transport at 4 o C.
Specimen Transport Instructions for Referring Laboratories
Instructions for Referral to CHLabs
Aliquot Instructions 500 uL Serum Fridge 4C
Aliquot Transport to CHL Fridge. Stable 7 days 2-8, if separated from cells.