Testing for Helicobacter pylori: Can stool provide the answer?

#Helicobacter pylori is a troublemaking bacterium that infects the stomach and can cause indigestion, stomach ulcers and, in rare cases, stomach cancer. H. pylori can be treated with antibiotics, but an accurate diagnosis of infection is important before starting treatment. Once the course of antibiotics is complete, a follow-up test is needed to make sure the H. pylori are history.

There are several different tests for H. pylori, and choosing the most appropriate test depends on the patient’s age and symptoms. For example, patients with symptoms of cancer will need an endoscopy—a camera in a tube inserted through their throat into the stomach—but other patients could be tested with less invasive methods. These methods include blood tests, urea breath tests, or stool tests. The stool tests are called stool antigen tests because they look for H. pylori antigens (bits of the H. pylori bacteria that stimulate our immune system).

Many experts consider urea breath testing to be the best non-invasive test for H. pylori, but it requires special equipment and is not readily accessible in rural and remote locations. In some areas of Canada, doctors and other health care providers use stool testing as the first option, saving patients the time and money it takes to travel outside their communities. However, this practice is not consistent across the country—many patients are still referred to larger city clinics or hospitals for urea breath testing.

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To clear up some of the uncertainty about which test to choose, #CADTH reviewed the evidence on H. pylori stool antigen tests to find out how accurate they are compared to other tests. CADTH is an independent agency that finds and summarizes the research on drugs, medical devices, and procedures.

CADTH review

For this project, CADTH found more than 200 publications in a literature search for publications between January 2009 and December 2014. Researchers narrowed down the list to 24 reports that were the most relevant. Of these, one report was a clinical practice guideline document, two were economic reports, and 21 were diagnostic studies—15 of which were for initial testing for suspected H. pylori infection and six of which were for follow-up testing after treatment.

Taking a look at all this research, CADTH found that many (but not all) of the stool antigen tests had good diagnostic sensitivity and specificity. In other words, many of the stool tests were good at correctly identifying people who had H. pylori (good sensitivity) and good at identifying those people who did not have H. pylori (good specificity).

Which type of stool antigen test is best?

There are several commercially available stool antigen tests for H. pylori that use either monoclonal or polyclonal antibodies. Monoclonal antibodies are more specific to H. pylori but more expensive to produce, while polyclonal antibodies are less specific but less expensive. With both types of tests, the antibody recognizes the H. pylori antigen, and this reaction causes the positive sample to turn a different colour. Some of the tests can be performed in the doctor’s office, with results available in a few minutes, but others need to be sent out to a lab.

The CADTH review showed that, generally, the monoclonal antibody tests performed better—the results from these tests were close to or just as accurate as the results from urea breath testing or endoscopy. Some of the polyclonal tests also performed well, but some showed lower sensitivity.

In particular, the stool tests that worked the best for initial diagnosis were:

Testmate pylori antigen [TPAg EIA] (a lab-based test using monoclonal antibodies)
Premier Platinum HpSA Plus (a lab-based test using monoclonal antibodies)
Amplified IDEIA Hp StAR (a lab-based test using monoclonal antibodies)
EZ-STEP H. pylori (a lab-based test using polyclonal antibodies)
Atlas H. pylori antigen (an in-office test using monoclonal antibodies)

The stool tests that performed the best for follow-up were:

Testmate rapid pylori antigen [Rapid TPAg] (an office-based test using monoclonal antibodies)
Testmate pylori antigen EIA [TPAg EIA](a lab-based test using monoclonal antibodies)
Amplified IDEIA Hp StAR (a lab-based test using monoclonal antibodies)
HpSA ELISA II (a lab-based test using monoclonal antibodies)
RAPID Hp StAR (an in-office test using monoclonal antibodies)
ImmunoCard STAT! HpSA (an in-office test using monoclonal antibodies)

The clinical guideline document included in the CADTH review aligned well with these findings because it recommends choosing a stool antigen test that is laboratory-based, validated, and with monoclonal antibodies. This test could be used reliably for the initial diagnosis and for the follow-up testing after antibiotic treatment.

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The two economic reports included in the review examined only specific situations, but they did find the stool antigen tests to be cost-effective in these situations, meaning they provided good value for money.

Who can benefit

These results are encouraging for rural and remote patients and their health care providers. There are also implications for developing countries and health care centres—in Canada or abroad—that want to provide less invasive testing options that could potentially offer cost-savings.

To learn more about CADTH, visit www.cadth.ca, follow us on Twitter: @CADTH_ACMTS, or talk to our Liaison Officer in your region: www.cadth.ca/contact-us/liaison-officers.