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Vitamin B12 (B12)

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EPIC Test Name

VITAMIN B12

EPIC Code

LAB67

Specimen Requirements

plasma
Minimum Volume:0.5 mL
Collection:Collect using standard laboratory procedures
Transport:Room Temperature ASAP
Stability:Room Temperature: 2 hours at 20-25 degrees C
Refrigerated: 48 hours at 4-8 degrees C
Frozen: 8 weeks at -20 degrees C
Container:LIT-GRN
Processing/Storage:Centrifuge, aliquot and freeze.
Rejection Causes:Hemolysis,
Insufficient Sample Volume, lipemic samples

Methods

Electrochemiluminescence

Turnaround Time

SpecimenTurnaround TimeFrequency
plasmaRoutine: 4 hours24/7

Reference Ranges

Electrochemiluminescence
All RangeUnit
211-946 pg/mLpg/mL

Clinical Indications

• Vitamin B12 (cyanocobalamin) is a water-soluble vitamin and is involved in many biological functions including erythropoiesis, DNA methylation, and a cofactor of various enzymes involved in the metabolism of methylmalonic acid (MMA) and homocysteine.
• Deficiency of vitamin B12 in humans can causes macrocytosis, megaloblastic anemia, and neuropathy. The most common occurring cases is vitamin B12 deficiency causing pernicious anemia, an autoimmune disease with autoantibodies against gastric parietal cell H+/K+-ATPase and resulting in reduction of IF. In addition, blocking autoantibodies binding to the vitamin B12–binding sites of IF preventing Vitamin B12–IF complex being recognized by the cubam complex in the distal ileum
• Vitamin B12 deficiency frequently causes macrocytic anemia, glossitis, peripheral neuropathy, weakness, hyperreflexia, ataxia, loss of proprioception, poor coordination, and affective behavioral changes. These manifestations may occur in any combination; many patients have the neurologic defects without macrocytic anemia.
• Serum methylmalonic acid and homocysteine levels are also elevated in vitamin B12 deficiency states.

Additional Information

• Patients who have received a vitamin B12 injection or radiolabeled vitamin B12 injection within the previous 2 weeks may have high serum vitamin B12 levels, which can interfere with this assay leading to falsely elevated results.
• Roche immunoassay uses the intrinsic factor in the reagent. Patients having anti-intrinsic factor antibodies (common in pernicious anemia) can lead to elevated vitamin B12 measurement values.

Common Synonyms

B12

Performed

Lab
Chemistry - Downtown

Interpretative Information

• Low vitamin B12 results (< 180 ng/L) may cause megaloblastic anemia and peripheral neuropathies.
• Test for autoantibodies to intrinsic factor can provide information on a potential cause of vitamin B12 malabsorption. For patients with negative autoantibodies, but symptomatic, tests for methylmalonic acid and/or homocysteine can be considered.
• For patients with serum vitamin B12 levels in a borderline range of suspected Vitamin B12 deficient, normal level of homocysteine is indicative of rule out vitamin B12 and folate deficiency in an asymptomatic patient. However, if the homocysteine assay’s specific is in concern, methylmalonic acid level can be measured as a more specific for cellular-level B12 deficiency and is not increased by folate deficiency.
• In patients being evaluated for vitamin B12 deficiency who have intrinsic factor blocking antibodies (IFBA), false elevations of vitamin B12 may occur due to IFBA interference, potentially obscuring a physiological deficiency of vitamin B12. If observed vitamin B12 concentrations are discordant with clinical presentation, measurement of methylmalonic acid (MMAS / Methylmalonic Acid, Quantitative, Serum) should be considered.

CPT

82607

LOINC

2132-9

References

1. H Toh, IR van Driel, PA Gleeson: Pernicious anemia. N Engl J Med. 337:1441-1448 1997 9358143
2. AR Battersby: How nature builds the pigments of life: the conquest of vitamin B12. Science. 264:1551-1557 1994 8202709
3. SP Stabler: Vitamin B12 deficiency. N Engl J Med. 368:2041-2042 2013
4. S Saxena, R Carmel: Racial differences in vitamin B12 levels in the United States. Am J Clin Pathol. 88:95-97 1987 3604990
5. CR Kapadia: Vitamin B12 in health and disease: part I–inherited disorders of function, absorption, and transport. Gastroenterologist. 3:329-344 1995 8775094
6. R Carmel: How I treat cobalamin (vitamin B12) deficiency. Blood. 112:2214-2221 2008 18606874
7. BC Herzlich, TD Schiano, Z Moussa, et al.: Decreased intrinsic factor secretion in AIDS: relation to parietal cell acid secretory capacity and vitamin B12 malabsorption. Am J Gastroenterol. 87:1781-1788 1992 1449141
8. W Herrmann, H Schorr, R Obeid, et al.: Vitamin B-12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians. Am J Clin Nutr. 78:131-136 2003 12816782
9. R Grasbeck: Imerslund-Grasbeck syndrome (selective vitamin B(12) malabsorption with proteinuria). Orphanet J Rare Dis. 1:17 2006 16722557

Contact Information

Chemistry - Downtown: (315)464-4460
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