Developed and described by a team of investigators from the University of California, Davis, and Lawrence Livermore National Laboratory, the test is touted to be more accurate and simple. Unless, of course, you consider the use of a $2 million accelerator mass spectrometer to be a hurdle in the test. And then there are some specially designed bacteria:
The current definitive test for pernicious anemia, called the Schilling test, involves the ingestion of a low but significant amount of radiation and the collection of all urine produced in a 24-hour period. In contrast, the new test uses a single drop of blood and involves negligible radiation exposure – an amount equivalent to that received on a cross-country flight.
To measure vitamin B12 absorption with the new test, the researchers had a healthy male subject drink water containing 1.5 micrograms of purified carbon-14-labeled vitamin B12 (14C- B12), an amount of vitamin B12 equivalent to that found in a 2-ounce steak. Blood samples were taken every hours for the first 12 hours, and then less frequently thereafter to assess absorption of the labeled vitamin. The blood samples were then analyzed at Lawrence Livermore National Laboratory using an accelerator mass spectrometer, a sophisticated instrument that counts single atoms of 14C.
The UC Davis researchers collaborated to create the microscale system in bacteria that produced the 14C- B12 compound and evaluated absorption in a human subject. The team included nutritional biochemists Stephen R. Dueker and Colleen Carkeet at the School of Agricultural and Environmental Sciences, who worked with microbiologists John Roth and Peter Anderson from the College of Biological Sciences to synthesize the new compound in Salmonella enterica, a bacterium that normally produces B12 under anaerobic conditions. It also included Green and Joshua Miller, B and B12 vitamin experts from the School of Medicine, and nuclear physicist Bruce Buchholz at Lawrence Livermore National Laboratory, who designed dosimetry and conducted the accelerator mass spectrometry studies.
“I knew it was technologically possible to create 14C-B12 and use it to measure levels of the vitamin in blood via accelerator mass spectrometry,” said Dueker. “But we were having difficulty finding a strain of bacteria to produce the vitamin with the 14C in just the right place.”
That’s when they turned to fellow microbiology professor John Roth and his postdoctoral fellow Peter Anderson, who was working on a strain of Salmonella bacteria that turned out to be perfect for creating 14C-B12.
“We turned this bacteria into a micromachine for making labeled B12,” said Anderson. “The strain of bacteria was so efficient, that it converted all the labeled material it was given into 14C-B12. Vitamin B12 is one of nature’s most complex substances. By harnessing the power of bacteria, we were able to create the test…”