Test used to diagnose B12 deficiency may be inadequate

Published on October 28, 2004 at 9:14 AM · No Comments

A test that generally is used to measure the amount of vitamin B12 in the body is not sensitive enough to detect a deficiency of the vitamin, which has been linked to several neurological conditions, according to Saint Louis University research.

The findings were presented this month at a meeting of the American Neurological Association.

"B12 deficiency is associated with dementia, peripheral neuropathy and spinal cord disease," says Florian Thomas, M.D., Ph.D., associate professor of neurology at Saint Louis University School of Medicine and a researcher on the project.

"While it occurs at any age, B12 deficiency is more common in the elderly, may affect some vegetarians and their newborns, can be provoked by laughing gas anesthesia and also by a unique form of recreational drug use. Importantly, it is very easy to treat by taking one pill per day for life. We need to do a better job of detecting the problem."

Thomas and his Saint Louis University colleagues, Laurence J. Kinsella, M.D., associate professor of neurology, and Jamie T. Haas, M.D., a neurology resident, found that the standard test for B12 deficiency -- measuring its blood level -- may be too insensitive.

The scientists found that of 34 patients who had normal levels of B12, 26 had elevated levels of methylmalonic acid (MMA), which indicated B12 deficiency.

They are urging doctors who suspect their patients lack the vitamin to also test for levels of MMA, a natural compound in the body that increases when B12 is lacking.

"The usual way of diagnosing B12 deficiency may be inadequate because it underestimates the frequency of the problem, which is present in up to 20 percent of the elderly," Thomas says. "The problem is eminently treatable at pennies a day."

Dr. Kinsella has had a longstanding interest in B12 deficiency and its relationship to nitrous oxide, a general anesthetic in common use in dental offices and hospital operating rooms. A B12 deficiency can be caused by nitrous oxide, also known as laughing gas, by inhibiting the action of B12 when tissue stores are low.

"This becomes a public health problem in the elderly undergoing surgery or dental work who may have undiagnosed and untreated B12 deficiencies. It also occurs among dental personnel and others who repeatedly abuse nitrous oxide for its euphoric effects," he says.

Nitrous oxide abuse in the form of "whippets" or "whippits" occurs among medical personnel, teenagers and young adults who purchase nitrous oxide containers from baking supply stores or use the gas contained in whipped cream dispensers (hence the name), says Kinsella.

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