Vitamin B12 testing is performed on all samples.
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 Nutrition Examination Survey (NHANES) opted to use the combination of serum total vitamin B12 and methylmalonic acid (MMA) to monitor B12 status in the United States population.35 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 (in this case MMA) is performed only when the outcome of the first-line assay (vitamin B12 level) falls in an "equivocal" range.1,7 It has been suggested that borderline B12 levels (200-400 ng/L) should be followed up with measuring MMA levels.1 MMA levels below the upper limit of the reference interval (0-378 nmol/L) are strongly suggestive of normal B12 status.
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.
Immediately following collection, thoroughly mix sample by gently inverting 5 times
Gold serum separator (SST) tube
Room temperature (preferred) - 7 days
Refrigerated - 7 days
Frozen - 14 days
Freeze/thaw cycles -stable x3
Electrochemiluminescence immunoassay (ECLIA); reflex Liquid chromatography/tandem mass spectrometry (LC/MS-MS); Immunochemiluminometric assay (ICMA); Enzyme-linked immunosorbent assay (ELISA)
B12 pg/mL 232-1245 pg/mL
Methylmalonic acid, serum: 0 - 378 nmol/L
Intrinsic factor Abs, serum: 0.0 - 1.1 AU/mL
Antiparietal cell Ab: 0.0 - 20.0 Units