Clotted blood tube (Serum gel separator clot activator tube)

Minimum blood volume: 5 mL

Paediatric clotted blood tube

Number of vials: 2

Minimum blood volume: 1.6 mL

Authorisation code required

No

Active B12 ≤ 24 pmol/L detected vitamin B₁₂ deficiency with a specificity of 95%.

To diagnose vitamin B₁₂ deficiency.

Vitamin B₁₂ in serum is bound to two proteins, transcobalamin (TC) and haptocorrin (HC). The transcobalamin-vitamin B₁₂ complex is called holotranscobalamin (HoloTC), which represents the biologically active form of vitamin B₁₂ (Active B12) as only this fraction of vitamin B₁₂ can be taken up from the blood into the cells of the body.

The measurement of serum total vitamin B₁₂ mostly reflects the fraction of metabolically inert vitamin B₁₂ that is bound to HC, holohaptocorrin (HoloHC), while Active B12 consists of 10 - 30% of total vitamin B₁₂. Due to the shorter circulating half-life of HoloTC compared to HoloHC, decreased serum Active B12 level is regarded as an early marker of vitamin B₁₂ deficiency and has been reported to have comparable or modestly superior diagnostic accuracy compared with total vitamin B₁₂ based on receiver operating curve analysis using serum methylmalonic acid > 450 µmol/L as gold standard.

Serum Active B12 levels are low in patients with clinical and laboratory findings for B₁₂ deficiency which include neurological abnormalities, megaloblastic anaemia and increased excretion of methylmalonic acid (MMA). The impaired DNA synthesis associated with vitamin B₁₂ deficiency causes macrocytic anaemias that are characterised by abnormal maturation of erythrocyte precursors in the bone marrow, which results in the presence of megaloblasts and in decreased erythrocyte survival.

Pernicious anaemia is a macrocytic anaemia caused by vitamin B₁₂ deficiency that is due to lack of intrinsic factor. Low vitamin B₁₂ intake, gastrectomy, diseases of the small intestine, malabsorption, and trans-cobalamin deficiency can also cause vitamin B₁₂ deficiency.

Active B12 reflect vitamin B₁₂ status, independent of recent absorption of the vitamin.