Helicobacter pylori infection diagnostic test

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Yamuna Kondapally, M.B.B.S [2]

Overview

The nonendoscopic diagnostic testing methods for H. pylori include antibody tests, urea breath test and fecal antigen test.

Antibody testing is inexpensive and widely available but poor PPV in populations with a low prevalence of H. pylori infection limits its usefulness in clinical practice.
The UBTs and fecal antigen tests provide reliable means of identifying active H. pylori infection before antibiotic therapy.
The UBT is the most reliable nonendoscopic test to document eradication of H. pylori infection.
The monoclonal fecal antigen test provides another nonendoscopic means of establishing H. pylori cure after antibiotic treatment.
Testing to prove H. pylori eradication appears to be most accurate if performed at least 4 wk after the completion of antibiotic therapy.

The nonendoscopic diagnostic testing methods for H.pylori include:

Antibody testing depends on the detection of H.pylori specific IgG antibodies in serum, whole blood, or urine.^[1]
The IgG antibodies typically become detected 21 days after infection and can remain present long after eradication.
Antibodies are detected using enzyme-linked immunosorbent assay (ELISA) and latex agglutination techniques.

The urea labeled with either the nonradioactive isotope 13C or the radioactive isotope 14C is ingested.
The H.pylori urease converts labeled urea to CO2, which can be quantitated in expired breath.

The urea breath test has 95% sensitivity and specificity.

This test is an accurate means of post-treatment testing.
As this test mainly depends on urease activity of H.pylori, the sensitivity of the test is decreased by medications such as bismuth containing products, PPIs, and antibiotics as they reduce organism density or urease activity. It is recommended to withhold PPIs for 7-14 days prior to the test, and bismuth and antibiotics are withheld for at least 28days.
Antacids do not affect the efficacy of the test.

The fecal antigen test (FAT) is an enzyme immunoassay which identifies H.pylori antigen with the use of polyclonal anti-H.pylori antibody.
Monoclonal antibodies can also be used to identify fecal H.pylori antigens.
Both tests are used to screen for infection and post-treatment testing.
Fecal antigen test is approved by U.S Food and Drug Administration as an alternative means of establishing H.pylori cure to urea breath test.
The polyclonal test has excellent sensitivity, specificity, and predictive values before treatment but less satisfactory after the treatment.
This test may be effective in confirming eradication of H.pylori infection as early as 14 days after treatment. However, it is suggested that it should be done more than 4 wk and up to 8-12 wk after h.pylori treatment.
The sensitivity of the test is affected by the use of PPIs, bismuth compounds, and antibiotics. The specificity is affected by the bleeding peptic ulcer disease.

Nonendoscopic testing	Advantages	Disadvantages
1. ELISA serology (quantitative and qualitative)	Inexpensive and widely available Very good NPV Sensitivity (85-92%) and specificity (70-83%)	PPV dependent upon background H. pylori prevalence. Not recommended after H. pylori therapy Less accurate and does not identify infection
*2. Urea breath tests (13C and 14C)	Identifies active H. pylori infection. Excellent PPV and NPV regardless of H. pylori prevalence. Useful before and after H. pylori therapy Sensitivity (95%) and specificity (96%)	Reimbursement and availability remain inconsistent
*3. Fecal antigen test	Identifies active H. pylori infection. Excellent positive and negative predictive values regardless of H. pylori prevalence. Useful before and after H. pylori therapy Sensitivity (95%) and specificity (94%)	Polyclonal test less well validated than the UBT in the posttreatment setting. The monoclonal test appears reliable before and after antibiotic therapy. Unpleasantness associated with collecting stool