Letters
Ageing Hematologic diseases Medical practices Statistics
Volume 197 - Issue 8

Vitamin B12 screening in older inpatients without known risk factors: why do clinicians measure it?

Authors:  Celia S M Ting, John C Oldroyd and Michele R Levinson

Med J Aust 2012; 197 (8): 442-443. || doi: 10.5694/mja11.11516
Published online: 15 October 2012

Tests for serum vitamin B12 and red cell folate levels are commonly requested in elderly inpatients to rule out reversible causes of cognitive impairment (eg, delirium). This imposes some cost on the community. The evidence for the association of cognitive impairment and vitamin B12 deficiency is inconclusive. It is also unclear whether other markers, such as elevated mean corpuscular volume (MCV) and ...

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To the Editor: Tests for serum vitamin B12 and red cell folate levels are commonly requested in elderly inpatients1 to rule out reversible causes of cognitive impairment (eg, delirium).2 This imposes some cost on the community. The evidence for the association of cognitive impairment and vitamin B12 deficiency is inconclusive.3,4 It is also unclear whether other markers, such as elevated mean corpuscular volume (MCV) and anaemia, can indicate the need for vitamin B12 testing in elderly inpatients without known risk factors for vitamin B12 deficiency (such as coeliac disease and pernicious anaemia).

We report the results of a cross-sectional study (5 October 2009 to 6 October 2010) of elderly inpatients aged 65 years and over with low risk of vitamin B12 deficiency. We assessed 1) the prevalence of vitamin B12 deficiency using holotranscobalamin; 2) whether cognitive impairment (delirium) was associated with vitamin B12 deficiency; and 3) whether other biochemical markers could be used to indicate B12 deficiency.

Vitamin B12 deficiency was defined biochemically as serum holotranscobalamin level less than 23 pmol/L, or serum holotranscoba-lamin level between 23 pmol/L and 35 pmol/L with fasting plasma homocysteine concentration less than 12 μmol/L. Acute delirium was diagnosed by a geriatrician and given a score using the Confusion Assessment Method.

Of 184 participants (mean age, 78.3 years), 25 (14%) had vitamin B12 deficiency and six (3%) had delirium. Holotranscobalamin levels and delirium were unassociated. In total, 20 participants (11%) had iron deficiency (ferritin level under 30 ng/mL) and two (1%) had low folate levels (red cell folate level under 800 nmol/L). Of those with vitamin B12 deficiency, five (20%) had iron deficiency and one (4%) had a high MCV. Among 20 participants with iron deficiency, five (25%) had a vitamin B12 deficiency and all 20  had a normal MCV.

Vitamin B12 deficiency in low-risk asymptomatic elderly inpatients was relatively high (14%) in our study. The incidence of delirium was low (3%), and no association was found between vitamin B12 deficiency and delirium. This confirms clinical suspicions that measuring vitamin B12 levels is not helpful in the diagnosis or management of delirium. Vitamin B12 deficiency and iron deficiency may coexist in the same individual, although evidence for using high MCV to predict vitamin B12 deficiency is limited. The long-term clinical significance of subclinical vitamin B12 deficiency is unknown.

Authors

  • Celia S M Ting1
  • John C Oldroyd1
  • Michele R Levinson1
  • 1. Cabrini Institute, Cabrini Health, Melbourne, VIC.

Correspondence: drtingcelia@gmail.com

Competing interests

No relevant disclosures.

References

View this article on Wiley Online Library