A safer, more accurate test for vitamin B-12 deficiency -- which affects about a million Americans over the age of 65 -- has been developed by researchers at UC Davis and the Lawrence Livermore National Laboratory.

An inability to properly absorb vitamin B-12 causes pernicious anemia, leading to fatigue and neurological problems. But physicians lack a safe and simple way to test for poor vitamin B-12 absorption in their patients.

"If you can make the diagnosis, the treatment is easy and the damage can be reversed. But, making the diagnosis is tricky," said Ralph Green, professor and chair of pathology and laboratory medicine at UC Davis.

The new test involves drinking a small amount of vitamin B-12 labeled with radioactive carbon 14 (14C) and collecting a single drop of blood. The amount of 14C-labeled vitamin B-12 in the sample is measured with an accelerator mass spectrometer, which can count single atoms of 14C. The radiation dose involved is equivalent to that received on a cross-country flight.

The labeled vitamin B-12 was made using a strain of Salmonella enterica bacteria developed by John Roth, professor of microbiology, and postdoctoral researcher Peter Anderson at the College of Biological Sciences.

Vitamin B-12 is one of the most complex substances in nature, Anderson said. Using the bacteria, the researchers had an efficient way to make the new compound for the test.

The researchers hope to license the patented technology to a company that will make the test available to physicians.

Other members of the research group are: Jozsef Lango, lecturer at the School of Veterinary Medicine; Bruce Buchholz, physicist at LLNL; Joshua Miller, adjunct professor at the School of Medicine; and Bruce Hammock, professor of entomology. The research was supported with grants from the National Institutes of Health's National Center for Research Resources and the National Institute of Environmental Health Sciences.