By Melanie Fridl Ross
GAINESVILLE, Fla.---University of Florida researchers report a blood test they helped develop can accurately detect the bacteria that causes most ulcers -- at less than one-fourth the cost of endoscopy, the standard diagnostic tool.
Unlike other blood tests, which only tell a doctor the bacteria has infected the patient at some point, this new test confirms the presence of an active infection, data from a pilot study show.
The ongoing National Institutes of Health-funded research is a spin-off of other projects that earlier this year led to Food and Drug Administration approval of a new breath test, currently offered at the Shands GI Diagnostic Laboratory. Both the blood and breath tests screen for the bacterium Helicobacter pylori.
The majority of patients who have so-called "peptic" ulcers of the stomach or the duodenum -- the place where the stomach meets the small intestine -- are infected with H. pylori. The organisms reside in or under the mucus layer lining the stomach and intestines, said gastroenterologist Phillip Toskes, chairman of the department of medicine at UF's College of Medicine.
"The big news has been that this bacterium, H. pylori, causes most ulcers," he said. "We had an idea that this diagnosis could be made in a new way."
For many patients, the prospect of a simple blood test is an attractive alternative to the standard invasive approach doctors use -- a procedure known as an endoscopy to biopsy the stomach and detect H. pylori. Endoscopy is costly and can be uncomfortable, Toskes said.
"Endoscopy is a very good test and patients with complicated ulcer disease still need it, but many patients with ulcer disease do not experience bleeding or do not have obstructions, and they can easily be diagnosed with this simple blood test," he said.
Here's how the new blood test works: Physicians draw a small blood sample after giving the patient a compound to drink called urea, which has a nonradioactive tag. H. pylori converts urea into carbon dioxide. Essentially, doctors can measure changes in labeled carbon dioxide levels in the blood within minutes to see whether bacteria are actively metabolizing the urea.
During the past year, UF researchers studied 60 people who had unexplained abdominal pain. If they were candidates, they were enrolled in the study and underwent an initial biopsy performed by endoscopy to look for the bacteria. The group was then divided into those who had the bacteria and those who didn't. All then received the 13C labeled urea breath test, followed by a 13C labeled urea blood test.
Neither the researchers nor the participants were told which group tested positive for the bacterium. The results, analyzed at an independent laboratory, showed the new blood test was highly accurate -- identifying the bacteria's presence greater than 95 percent of the time -- as good as the breath test or standard biopsy.
The breath test works on similar principles. Patients ingest 13C urea, then blow into a bag. The breath sample is sent to Shands at UF to screen for 13C carbon dioxide levels, which signal the presence of H. pylori.
"Like the blood test, the breath test is simple, relatively inexpensive and saves the patient the discomfort of endoscopy," Toskes said. "You can make the diagnosis and after you treat the patient, if the breath test is normal, it shows you have eradicated the bacterium. Physicians, however, are just not comfortable with breath tests."
In contrast, endoscopy requires patients to fast the night before the procedure. They then are sedated while a fiber-optic scope is inserted down the esophagus into the stomach and small intestine. Recovery takes several hours.
On average, the procedure costs about $1,000, Toskes said, while the breath test is only $200 to $300. The blood test could be even less expensive, representing significant savings, he said. "We have an opportunity if we can make this diagnosis appropriately to really go a long way toward eradicating ulcer disease in most patients," Toskes said. "For the first time we can cure it -- antibiotics kill the bacterium at a rate above 90 percent of the time. Very few new infections are occuring in the U.S. right now because of better sanitation. This disease could largely disappear."
The study's next phase -- a multicenter, national trial -- will begin in January. UF researchers, who are receiving NIH funds for these projects, will lead it. Other participating sites include Sinai Hospital in Detroit, Syracuse University, the University of Michigan, the University of South Carolina-Columbia and the University of Southern California.
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