Diagnosing vitamin B-12 deficiency on the basis of serum B-12 assay

doi:10.1136/bmj.333.7564.385

BMJ 2006;333:385-386 (19 August), doi:10.1136/bmj.333.7564.385

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Diagnosing vitamin B-12 deficiency on the basis of serum B-12 assay

Vinod Devalia, consultant haematologist¹

¹ Princess of Wales Hospital, Bridgend CF31 1RQ Vinod.Devalia@bromor-tr.wales.nhs.uk

The first 150 words of the full text of this article appear below.

Serum vitamin B-12 concentrations are measured to assess thepresence of its deficiency in patients presenting with haematolological,neurological, and neuropsychiatric abnormalities. Replacementtherapy is instituted promptly, particularly to prevent irreversibleneurological and cognitive dysfunction.

I present two cases with paradoxical vitamin B-12 results, whichhighlight the fallacies of the serum vitamin B-12 assay andemphasise the importance of taking into account the overallclinical picture before prejudging the significance of the vitaminB-12 assay result.

A 59 year old white woman was seen urgently for assessment ofa macrocytic anaemia. She had normal serum B-12 concentrations,confirmed on three occasions. She complained of progressivelyincreasing lethargy, palpitations, and buzzing in the ears overabout three months. She had a good, well balanced diet and wasnot a vegetarian. Apart from thyroxine, she was taking no regularmedication. She said her father had had pernicious anaemia.On clinical examination the . . . [Full text of this article]

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Rapid Responses:

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Low B12 results are common . Pragmatic solutions: john sharvill
bmj.com, 21 Aug 2006 [Full text]
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Further cases of false normal B12 assays - intrinsic factor antibody interference a possible mechanism?: Malcolm S Hamilton, et al.
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Two other common scenarios where the clinical picture is of utmost importance when interpreting a vitamin B-12 assay result: Adam P Morton
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Author's reply: Vinod Devalia
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Management of atypical haematological forms of vitamin B12 deficiency: Emmanuel ANDRES
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Re: Over diagnosis and treatment of B12 deficiency in primary and secondary care?: Mary G Gibbs
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