Document Detail

Measurement of total vitamin B12 and holotranscobalamin, singly and in combination, in screening for metabolic vitamin B12 deficiency.
MedLine Citation:
PMID:  16384886     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: The standard screening test for vitamin B12 deficiency, measurement of total plasma vitamin B12, has limitations of sensitivity and specificity. Plasma vitamin B12 bound to transcobalamin (holoTC) is the fraction of total vitamin B12 available for tissue uptake and therefore has been proposed as a potentially useful alternative indicator of vitamin B12 status.
METHODS: We compared the diagnostic accuracy of total vitamin B12, holoTC, and a combination of both measures to screen for metabolic vitamin B12 deficiency in an elderly cohort (age > or = 60 years). Plasma methylmalonic acid and homocysteine were used as indicators of vitamin B12 deficiency.
RESULTS: Low total vitamin B12 (< 148 pmol/L) and low holoTC (< 35 pmol/L) were observed in 6.5% and 8.0%, and increased methylmalonic acid (> 350 nmol/L) and homocysteine (> 13 micromol/L) were observed in 12.1% and 17.0% of the study participants. In multiple regression models, holoTC explained 5%-6% more of the observed variance in methylmalonic acid and homocysteine than did total vitamin B12 (P < or = 0.004). ROC curve analysis indicated that total vitamin B12 and holoTC were essentially equivalent in their ability to discriminate persons with and without vitamin B12 deficiency. Individuals with low concentrations of both total vitamin B12 and holoTC had significantly higher concentrations of methylmalonic acid and homocysteine than did individuals with total vitamin B12 and/or holoTC within the reference intervals (P < 0.001).
CONCLUSIONS: HoloTC and total vitamin B12 have equal diagnostic accuracy in screening for metabolic vitamin B12 deficiency. Measurement of both holoTC and total vitamin B12 provides a better screen for vitamin B12 deficiency than either assay alone.
Joshua W Miller; Marjorie G Garrod; Alan L Rockwood; Mark M Kushnir; Lindsay H Allen; Mary N Haan; Ralph Green
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2005-12-29
Journal Detail:
Title:  Clinical chemistry     Volume:  52     ISSN:  0009-9147     ISO Abbreviation:  Clin. Chem.     Publication Date:  2006 Feb 
Date Detail:
Created Date:  2006-02-01     Completed Date:  2006-03-10     Revised Date:  2014-09-21    
Medline Journal Info:
Nlm Unique ID:  9421549     Medline TA:  Clin Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  278-85     Citation Subset:  IM    
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MeSH Terms
Aged, 80 and over
California / epidemiology
Cohort Studies
Mass Screening
Middle Aged
Transcobalamins / analysis*
Vitamin B 12 / blood*
Vitamin B 12 Deficiency / blood,  diagnosis*,  epidemiology
Grant Support
Reg. No./Substance:
0/Transcobalamins; P6YC3EG204/Vitamin B 12

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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