WHEN TO TEST FOR H PYLORI ...
Empiric treatment for H pylori is not recommended. Thus, testing is indicated for patients who have risk factors for the bacterium or who fail to respond to acid suppression therapy. There are various ways to test for H pylori. Which test you choose depends, in part, on patient-specific factors.
Serology. IgG serology testing is extremely useful in patients who have never been diagnosed with H pylori. It is best suited for those who are currently taking PPIs or who recently completed a course of antibiotics, since neither medication affects the results of the serology test.
Serology testing should not be used, however, for any patient who was previously diagnosed with or treated for H pylori, because this type of test cannot distinguish between active and past infection. The IgG serology test has a sensitivity of 87% and a specificity of 67%.30
Stool antigen. Stool tests using monoclonal antibodies to detect the presence of H pylori have a sensitivity of 87% to 92% and a specificity of 70%. Stool antigen is also an excellent post-treatment test to confirm that H pylori has been eradicated.31
Stool testing has some drawbacks, however. PPIs can decrease the sensitivity and should be discontinued at least two weeks prior to stool testing.32 In addition, a stool test for H pylori is not accurate if the patient has an acute GI bleed.
Urea breath testing. This is the most sensitive and specific test for active H pylori infection (90%-96% sensitivity and 88%-96% specificity).33 PPIs can lower the sensitivity of the test, however, and are typically discontinued at least two weeks prior to testing. Urea breath testing, like stool testing, is an excellent way to confirm that H pylori has been eradicated after treatment. However, it is more expensive than other tests for H pylori and often inconvenient to obtain.13
An EGD is indicated for a patient who has failed to respond to acid suppression therapy and has a negative serology, stool antigen, or urea breath test for H pylori.
Biopsy-based testing for H pylori is performed with EGD and is therefore reserved for patients who have red flags or other indications of a need for invasive testing. There are three types of biopsy-based tests: urease (sensitivity, 70%-90% and specificity, 95%); histology (87%-92% and 70%, respectively); and culture (85%-88% and 69%, respectively). Overall, the specificity is slightly better than that of noninvasive testing, but the sensitivity can be lowered by recent use of PPIs, bismuth, or antibiotics.12,34
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