Clarke et al proposed an evaluation of an elderly patient for vitamin B12 or folate deficiency. The authors are from the University of Oxford, University of Bergen (Norway), Trinity College Dublin, and Aarhus University (Denmark).
Some facts about vitamin B12 and folate in an elderly patient:
(1) An elderly patient may show signs and symptoms of vitamin B12 or folate deficiency despite a serum level above the lower limit of normal.
(2) Functional deficiency in folate can result in an elevated serum homocysteine level. Functional deficiency in vitamin B12 can result in elevations of serum homocysteine and methylmalanic acid.
(3) Renal impairment can result in elevated serum methylmalonic acid levels due to impaired clearance. This cause of elevated serum methylmalonic acid levels does not respond to vitamin B12 deficiency.
(4) Diagnosis of deficiency in vitamin B12 or folate can be difficult. The best measure is a decrease in homocysteine and/or methylmalonic acid and improvement in clinical symptoms following vitamin replacement.
Finding
Recommendation
vitamin B12 or folate below normal
Replace deficient vitamin and identify cause if possible.
vitamin B12 low normal
Measure homocysteine and methylmalonic acid. If elevated treat with vitamin B12 and monitor response.
folate low normal
Measure homocysteine. If elevated treat with folate and monitor response
where:
• If expense is an issue, then measurement of homocysteine only will detect most vitamin B12 deficiencies associated with low normal serum levels.
• A value between the lower limit of normal and the mean for the reference range will be used to detect low normal levels.
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