Vitamin B12 Assay, Serum
Use
The Vitamin B12 assay is primarily used for the investigation of macrocytic anemia and for the workup of deficiencies observed in megaloblastic anemias. Vitamin B12, also known as cobalamin, is vital for hematopoiesis and normal neuronal function. It is acquired solely from animal proteins and relies on intrinsic factor for proper absorption. Deficiency in vitamin B12 can lead to macrocytic anemia, glossitis, peripheral neuropathy, and various neurological manifestations such as ataxia, weakness, and behavioral changes. Serum methylmalonic acid and homocysteine levels often rise in cases of vitamin B12 deficiency.
Special Instructions
Patients should be asked if they have received a vitamin B12 injection or radiolabeled vitamin B12 injection within the last 2 weeks, as results will not reflect deficiency or malabsorption. If such an injection has been received in the past 2 weeks, this test should not be ordered. Furthermore, the test only measures serum B12 and should be followed up with ACASM / Pernicious Anemia Cascade, Serum for a comprehensive assessment.
Limitations
This test should not be performed on patients who have recently received a vitamin B12 injection, as it may cause elevated results that do not reflect true deficiency. Additionally, numerous substances can affect serum vitamin B12 levels, such as vitamins C and A, estrogens, and anticonvulsants. Interference from intrinsic factor blocking antibodies can lead to false elevation, obscuring true physiological deficiency. Moreover, patients with antibody interference should consider follow-up testing for methylmalonic acid for confirmation.
New York Approved
Methodology
Immunoassay (Other)
Biomarkers
LOINC Codes
- 2132-9
- 2132-9
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
0.6 mL
Minimum Volume
0.5 mL
Container
Plastic vial
Collection Instructions
Serum gel tubes should be centrifuged within 2 hours of collection. Red-top tubes should be centrifuged and the serum aliquoted into a plastic vial within 2 hours of collection.
Patient Preparation
This test should not be performed on patients who have received a vitamin B12 injection or radiolabeled vitamin B12 injection within the previous 2 weeks.
Causes for Rejection
Gross hemolysis
Stability Requirements
| Temperature | Period |
|---|---|
| Refrigerated | 7 days |
| Frozen | 90 days |