Helicobacter pylori Infection — Testing Options for Accurate Diagnosis and Management
Helicobacter pylori (H pylori) infection is extremely widespread, affecting approximately 50 percent of the world's population.1 While the overall prevalence in the United States is about 30%, prevalence in non-Hispanic blacks and Hispanic-Americans is 50% to 60%.2 Among immigrant groups from Southeast Asia, the prevalence can be as high as 80%.3
H pylori testing has primarily been recommended only for diagnosis, but the decline in treatment efficacy raises the question of whether to routinely test posttreatment. Dr. Neil Stollman, Northern California Gastroenterology Consultants, discusses options available for physicians to ensure accurate diagnosis and to confirm H pylori eradication.
In some parts of the world, particularly Southeast Asia and the Indian subcontinent the majority of the population has H pylori. In the United States, about a third of the population is affected.1. 2.“If you look at the overall number, we’re a relatively low risk country,” observes Dr. Stollman, “but there’s a wide range in prevalence depending on the particular group. Among the young, relatively affluent, and US born, there’s a very low prevalence¾about 5%¾while among certain immigrant groups, individuals of lower socioeconomic status, and certainly among the elderly, there’s a much higher prevalence. Among 80-year-old first generation immigrants from Southeast Asia, it’s probably about 75%.”
H. pylori causes illness in a subgroup of patients. “Most get gastritis, a proportion of those get dyspepsia, and a further subset (about 15%) get peptic ulcer disease,” notes Dr. Stollman. “A very small number¾less than one in one thousand¾will get gastric cancer. But, while most people with H. pylori don’t get cancer, most people with stomach cancer get it as a consequence of H. pylori.
While it hasn’t been definitively shown that early intervention reduces the incidence of cancer, if you look at populations that have eradicated it compared with those that haven’t, there does seem to be a reduced risk of cancer, if caught early. So, there are fairly good data that early treatment of H. pylori likely lowers the subsequent risk of gastric cancer.”
Testing for H pylori in the U.S. is usually only performed on symptomatic people. According to Dr. Stollman, there may be a few exceptions to this rule. “We may screen asymptomatic family members of stomach cancer patients. The bacterium is transmitted person-to-person, particularly from mother to child, so we may want to test the children of a woman with stomach cancer. Obviously, if someone has stomach cancer or an ulcer we test for H. pylori, and if someone has dyspepsia or a stomach ache, it’s rational to look for H. pylori.”
There are four kinds of tests for H pylori--one invasive and three noninvasive. Endoscopy coupled with biopsy is a test of active infection, but due to its cost and invasive nature, it would not usually be performed unless a patient already requires an endoscopy.
Serology--an Imperfect Test
The remaining three tests are noninvasive: serology, urea breath test (UBT), and stool antigen test. Dr. Stollman points out there’s an important distinction between serology and the other two tests. “Serology is a test of exposure, not infection,” he stresses. “The presence of antibodies in blood indicates you’ve been exposed to H pylori, but it doesn’t mean you actually have H pylori--you may or may not. While antibody serology is a good test to determine if you’ve ever had H pylori, it’s of no help in determining whether you currently have H pylori.”
“While serology may have a reasonable negative predictive value, a positive has a very poor positive predictive value,” continues Dr. Stollman. “This is particularly the case in a low-prevalence population, where a positive is more likely to be a false-positive. In this environment,its utility is worse than a coin flip.”
Urea Breath Test and Stool Antigen Test--Comparably Accurate, Not Equally Convenient
The other noninvasive tests, the urea breath test (UBT) and the stool antigen test, measure active infection and are recommended by the American Gastroenterological Association.4“They don’t culture the bacterium,” notes Dr. Stollman, “but for them to be positive, you have to have active infection. The breath test measures urease activity. Since the only thing in the stomach that could have urease activity is H pylori, the presence of urease activity implies active infection. The stool test identifies bacterial antigens in stool.”
Both tests are quite sensitive and quite specific. Their only limitation is that both require patients not to be taking proton-pump inhibitors (PPIs), antibiotics, or Pepto-Bismol®.”
Current guidelines for managing H pylori infection do not mandate posttreatment testing other than for patients who have had complications due to their infectionor for those whose symptoms persist. Dr. Stollman, however, believes follow-up testing is becoming increasingly important due to the decline in H pylori eradication rates. “Eradication rates have decreased radically over the last decade,” he notes. “From a level of 90% they’re now approaching 70%, largelydue to clarithromycin resistance. When treatment was 95% effective there was no compelling need to check, but if close to one in three people are failing treatment, you could make the case for retesting people routinely. In other words, as treatment gets less and less effective, retesting becomes more and more appropriate.”
When considering retesting,the difference between serology and the two other noninvasive tests becomes critical. “Serology is a completely unacceptable test for posttreatment testing, because antibodies don’t reliably go away,” stresses Dr. Stollman. “It’s an inappropriate test for confirmation of treatment, which is why it’s not recommended for post-therapy testing by either the American College of Gastroenterology or the American Gastroenterological Association. Both organizations recommend the breath test or the stool antigen test for this purpose”4, 5
- Brown L. Helicobacter pylori: epidemiology and routes of transmission. Epidemiol Rev. 2000;22:283-297.
- Everhart JE, Kruszon-Moran D, Perez-Perez GI, et al. Seroprevalence and ethnic differences in Helicobacter pylori infection among adults in the United States. J Infect Dis. 2000;181:1359-1363.
- Jones N, Chiba N, Goodman K. Helicobacter pylori in First Nations and recent immigrant populations in Canada. Can J Gastroenterol 2012 Feb; 26(2):97-103
- Chey WD, Wong BCY, and the Practice Parameters Committee of the American College of Gastroenterology Management of Helicobacter pylori Infection. American College of Gastroenterology. http://gi.org/guideline/management-of-helicobacter-pylori-infection/. Accessed November 6, 2013.
- Talley NJ, Vakil NB, Moayyedi P. American Gastroenterological Association technical review on the evaluation of dyspepsia. Gastroenterology. 2005;129:1756-1780.
Released on Monday, November 18, 2013