Specimen Collection

4.5 mL Plain Serum (Always Required)

Minimum volume of serum 500uL

4.5 mL Adult Heparin Blood

• Lithium Heparin - Non-gel (Green Cap)

4.5 mL Adult 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.

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.

Last updated at 10:45:13 25/01/2024