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Test Code B12 Vitamin B12

Additional Codes

Epic: LAB67

Specimen Required

Specimen Type: Serum

Collection Container/Type: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 3 mL

Collection Instructions: Centrifuge and separate cells after clot formation and within 4 hours of collection. 

Specimen Minimum Volume

0.5 mL

Specimen Stability

Room temperature: 3 days

Refrigerated : 7 days

Frozen: 3 months

Clinical Significance

Vitamin B12 is a member of the corrin family, and is a cofactor for the conversion of methylmalonyl Coenzyme-A to succinoyl CoA.  In addition, B12 is a cofactor in the synthesis of methionine from homocysteine, is implicated in the formation of myelin, and, along with folate, is required for DNA synthesis. Vitamin B12 is absorbed from food after binding to a protein call intrinsic factor, which is produced by the stomach.  Causes of B12 deficiency can be divided into three classes: nutritional deficiency, malabsorption syndromes, and other gastrointestinal causes. Vitamin B12 deficiency can cause megaloblastic anemia and can cause damage to the myelin sheath that surrounds and protects nerves, which may lead to peripheral neuropathy. People with intrinsic factor defects who do not get treatment eventually develop a megaloblastic anemia called pernicious anemia (PA).  A serum B12 level below the normal expected range may indicate that tissue B12 levels are becoming depleted.   Conditions associated with low serum B12 levels include iron deficiency, normal near-term pregnancy, vegetarianism, and partial gastrectomy/ileal damage, and Celiac disease, use of oral contraception, parasitic competition, pancreatic deficiency, treated epilepsy, and advancing age. Disorders associated with elevated levels of serum B12 include renal failure, liver disease, and myeloproliferative diseases.

Reference Range

211 - 911 pg/mL

Rejection Due To

Unlabeled, mislabeled, wrong tube type, hemolyzed, QNS, exceeds specimen stability requirements.

Day(s) and Time(s) Performed

Daily

Report Available

Same day

Method Name

Chemiluminescent microparticle immunoassay (CMIA)

LOINC

2132-9

Limitations

If the vitamin B12 results are inconsistent with clinical evidence, additional testing is suggested to confirm the result.
Heterophilic antibodies and RF in human serum can react with reagent immunoglobulins, interfering with in vitro immunoassay. Patients routinely exposed to animals or to animal serum products can be prone to this interference and anomalous values may be observed.
Hemolysis has been demonstrated to exhibit negative interference in this B12 assay. Hemolyzed specimens should not be analyzed. Specimens containing above normal protein concentrations may generate repeated (2 or more) “3350 Unable to process test-aspiration error for (Sample Pipettor) at (RV 24)” errors.  These specimens are unable to be tested using the ARCHITECT B12 assay. 
 

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