Vitamin B12 injections for the elderly
======================================

* Carl G. van Walraven
* C. David Naylor

**[The authors respond:]** 

We agree that treatment of true cobalamin (vitamin B12) deficiency is very important and should continue. We also agree that one might reasonably err on the side of overtreatment.

However, 2 issues regarding vitamin B12 deficiency must be considered when framing the problem of variations in utilization. First, as indicated by Francesco Ancllo, many of the symptoms of vitamin B12 deficiency are extremely nonspecific. Second, measurements of serum vitamin B12 levels do not discriminate between those patients with true vitamin B12 deficiency and those with low serum levels.1 We believe that the combination of nonspecific symptoms with a nonspecific laboratory test helps explain the large variations in parenteral vitamin B12 utilization between practices that we reported in our article.2

Anello raises several interesting points on which we would like to comment. First, the prevalence of biochemical evidence of vitamin B12 deficiency in the Framingham cohort was low.3 Review of Fig. 2 in the report by Lindenbaum and colleagues3 shows that 14 elderly patients with low serum levels of vitamin B12 had elevated serum methylmalonic acid levels. Since the cohort involved 548 elderly people, 2.5% showed biochemical evidence of vitamin B12 deficiency.

Second, the data reported by Yao and colleagues4 do not justify screening for vitamin B12 deficiency.[5, 6] Since 8% of the study participants had symptoms or signs of vitamin B12 deficiency prior to testing and would therefore have been tested on a case-finding basis, it does not appear that this was a general inception cohort. More generally, evidence for screening is lacking and is not recommended by others.7

Finally, the cost of vitamin B12 injections could be considerable at the population level. We used the database of the Ontario Drug Benefit program to identify all 34 264 elderly people who were prescribed parenteral vitamin B12 in 1996. Using claims in the Ontario Health Insurance Plan database, we calculated the direct cost of all physician visits associated with vitamin B12 injections in the year following the prescription date to be $4.2 million. This would pay for approximately 250 uncomplicated coronary artery bypass graft surgeries in elderly patients.8

Where should we go from here? First, we need further research using appropriate methodologies[9, 10] to find methods of determining true vitamin B12 deficiency. Second, the role of high-dose oral vitamin B12 supplementation needs elucidation.[11–13] Finally, since low serum levels do not necessarily equate with vitamin B12 deficiency, we need natural history studies and rigorous intervention trials to determine the most effective and efficient way to manage patients with nonspecific symptoms and low serum vitamin B12 levels.

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2.  2. van Walraven CG, Naylor CD. Use of vitamin B12 injections among elderly patients by primary care practitioners in Ontario. CMAJ 1999;161(2):146-9.
    
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