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The serum vitamin B12 level: its assay and significance.
Clin Haematol. 1976 Oct; 5(3):521-46.CH

Abstract

1. Low serum B12 levels can be measured with considerable precision by microbiological assay with the Euglena gracilis assay and B12 deficiency can be recognised with a high level of consistency by either the Euglena or L. leichmannii assays. Either method is ideally suited for the assay of large numbers of specimens. The Lactobacillus leichmanii technique requires preliminary extraction of protein and it has been suggested that this may be a source of inaccuracy. 2. The radioisotope dilution assay should be the ideal method of measuring B12 levels in small or moderate numbers of specimens for it is a simple method that can be carried out in any laboratory with suitable counting equipment. After many false starts the conditions required for accurate assay are now understood. Each of 40 to 50 radioisotopic dilution techniques that have been introduced claims to be capable of differentiating B12 deficiency from control subjects but the reported correlations between the actual levels found in the two different assays are variable and the levels may be much higher with some radioisotopic methods. 3. The subnormal serum levels which are found in pernicious anaemia with all these techniques indicate severe reduction of the liver B12 level. A low serum B12 level in other conditions has, in the absence of associated folate or iron deficiency, the same significance. If the fall in the serum B12 level is associated with folate or iron deficiency, the tissue B12 levels are usually reduced but not to the low levels found in B12 deficiency states. 4. In practice, a subnormal B12 level is a valuable pointer not only to unsuspected pernicious anaemia but also to other gastrointestinal or nutritional disorders. The significance of a fall in the B12 level can only be understood if its cause is defined by a full clinical and gastroenterological investigation. 5. Falsely low serum B12 levels are found under certain iatrogenic conditions and B12 levels may be normal in spite of cellular deficiency of B12 under the rare circumstances of pernicious anaemia being associated with chronic myeloid leukaemia or when there is deficiency of TC 2.

Authors

No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Review

Language

eng

PubMed ID

824083

Citation

Mollin, D L., et al. "The Serum Vitamin B12 Level: Its Assay and Significance." Clinics in Haematology, vol. 5, no. 3, 1976, pp. 521-46.
Mollin DL, Anderson BB, Burman JF. The serum vitamin B12 level: its assay and significance. Clin Haematol. 1976;5(3):521-46.
Mollin, D. L., Anderson, B. B., & Burman, J. F. (1976). The serum vitamin B12 level: its assay and significance. Clinics in Haematology, 5(3), 521-46.
Mollin DL, Anderson BB, Burman JF. The Serum Vitamin B12 Level: Its Assay and Significance. Clin Haematol. 1976;5(3):521-46. PubMed PMID: 824083.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The serum vitamin B12 level: its assay and significance. AU - Mollin,D L, AU - Anderson,B B, AU - Burman,J F, PY - 1976/10/1/pubmed PY - 1976/10/1/medline PY - 1976/10/1/entrez SP - 521 EP - 46 JF - Clinics in haematology JO - Clin Haematol VL - 5 IS - 3 N2 - 1. Low serum B12 levels can be measured with considerable precision by microbiological assay with the Euglena gracilis assay and B12 deficiency can be recognised with a high level of consistency by either the Euglena or L. leichmannii assays. Either method is ideally suited for the assay of large numbers of specimens. The Lactobacillus leichmanii technique requires preliminary extraction of protein and it has been suggested that this may be a source of inaccuracy. 2. The radioisotope dilution assay should be the ideal method of measuring B12 levels in small or moderate numbers of specimens for it is a simple method that can be carried out in any laboratory with suitable counting equipment. After many false starts the conditions required for accurate assay are now understood. Each of 40 to 50 radioisotopic dilution techniques that have been introduced claims to be capable of differentiating B12 deficiency from control subjects but the reported correlations between the actual levels found in the two different assays are variable and the levels may be much higher with some radioisotopic methods. 3. The subnormal serum levels which are found in pernicious anaemia with all these techniques indicate severe reduction of the liver B12 level. A low serum B12 level in other conditions has, in the absence of associated folate or iron deficiency, the same significance. If the fall in the serum B12 level is associated with folate or iron deficiency, the tissue B12 levels are usually reduced but not to the low levels found in B12 deficiency states. 4. In practice, a subnormal B12 level is a valuable pointer not only to unsuspected pernicious anaemia but also to other gastrointestinal or nutritional disorders. The significance of a fall in the B12 level can only be understood if its cause is defined by a full clinical and gastroenterological investigation. 5. Falsely low serum B12 levels are found under certain iatrogenic conditions and B12 levels may be normal in spite of cellular deficiency of B12 under the rare circumstances of pernicious anaemia being associated with chronic myeloid leukaemia or when there is deficiency of TC 2. SN - 0308-2261 UR - https://www.unboundmedicine.com/medline/citation/824083/The_serum_vitamin_B12_level:_its_assay_and_significance_ L2 - https://www.lens.org/lens/search/patent/list?q=citation_id:824083 DB - PRIME DP - Unbound Medicine ER -