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VITAMIN B12 DEFICIENCY PANEL
Test CodeLAB00119
Alias/See Also
Lab00119
LabCorp TC: 141503
Megaloblastic Anemia Cascade
Pernicious Anemia Casacade
LabCorp TC: 141503
Megaloblastic Anemia Cascade
Pernicious Anemia Casacade
Includes
Vitamin B12 testing is performed on all samples.
If Vitamin B12 is <200 pg/mL: Interinsic Factor Blocking Antibodies and Antiparietal Cell Antibodies will be performed.
If Vitamin B12 is between 200 and 400 pg/mL: Methylmalonic Acid will be performed.
If Methylmalonic Acid is >378 nmol/L: Intrinsic Factor Blocking Antibodies and Antiparietal Cell Antibody will be performed.
If Vitamin B12 is <200 pg/mL: Interinsic Factor Blocking Antibodies and Antiparietal Cell Antibodies will be performed.
If Vitamin B12 is between 200 and 400 pg/mL: Methylmalonic Acid will be performed.
If Methylmalonic Acid is >378 nmol/L: Intrinsic Factor Blocking Antibodies and Antiparietal Cell Antibody will be performed.
Preferred Specimen
3 mL of Serum
(Marble/Gold)
(Marble/Gold)
Patient Preparation
This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as Vitamin B7 or B8, Vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.
Minimum Volume
2 mL
Instructions
Separate serum from cells within two hour of collection and transfer to plastic transport tube.
Transport Temperature
Refrigerated
Specimen Stability
Refrigerated: 7 days
Limitations
Nintey percent of patients with pernicious anemia have gastric parietal cell antibodies, but specificity of this test is poor since they are also found in 15% of elderly subjects.
If IFA results are negative but suspicion for pernicious anemia remains, an elevated serum gastrin levle is consistent with the diagnosis.
Mutations in the gene encoding intrinsic factor, can also lead to an inherited form of B12 malabsorption and deficiency, which resembles pernicious anemia, but without autoantibody involvement.
In the presence of dicordance between laboratory test result and strong clinical features of B12 deficiency, it remains important to proceed with treatment to avoid neurological impairment.
Methylmalonic acid can increase (300-700 nmol/L) in renal failure and its refractory to B12 administration.
Some patients with gastric atrophy and diminished parietal cell function are not positive for IFA or PCA. Diminished acid secretion casused by gastric atrohpy regardless of the etiology can cause increased secretion of gastrin. Elevated gastrin levels can support the diagnosis of PA in antibody negative patients. It is important to diagnose hypergastrinaemia arising from loss gastric parietal cells drives development of antral enterochromaffin cell hyperplasia that can further develop into neoplasia and carcinoid syndrome.
If IFA results are negative but suspicion for pernicious anemia remains, an elevated serum gastrin levle is consistent with the diagnosis.
Mutations in the gene encoding intrinsic factor, can also lead to an inherited form of B12 malabsorption and deficiency, which resembles pernicious anemia, but without autoantibody involvement.
In the presence of dicordance between laboratory test result and strong clinical features of B12 deficiency, it remains important to proceed with treatment to avoid neurological impairment.
Methylmalonic acid can increase (300-700 nmol/L) in renal failure and its refractory to B12 administration.
Some patients with gastric atrophy and diminished parietal cell function are not positive for IFA or PCA. Diminished acid secretion casused by gastric atrohpy regardless of the etiology can cause increased secretion of gastrin. Elevated gastrin levels can support the diagnosis of PA in antibody negative patients. It is important to diagnose hypergastrinaemia arising from loss gastric parietal cells drives development of antral enterochromaffin cell hyperplasia that can further develop into neoplasia and carcinoid syndrome.
Clinical Significance
Diagnosis of Vitamin B12 Deficiency. Although often used as the first-line screening test for B12 deficiency, serum B12 measurement used in isolation has a generally poor sensitivity and specificity for detection of B12 deficiency. The National Health and Nutritiun Examination Survey opted to use the combination of serum total vitmain B12 and methylmalonic acid to monitor B12 status in the United States population. In the interest of economy, a number of groups have suggested the use of a sequential selection algorithm for the detection of B12 deficiency. In this approach, a second-line assay (vitamin B12) falls in an "equivocal" range. It has been suggested that boarderline B12 levels (200-400 ng/L) should be followed up with measuring methylmalonic acid levels. Methylmalonic acid levels below the upper limit of the reference range (0-378 nmol/L) are strongly suggestive of normal B12 status.
Performing Laboratory
LabCorp