From the Guidelines
A positive serum Helicobacter pylori (H. pylori) antibody test does not necessarily indicate an active infection, as antibodies can persist for years after the infection has been successfully treated or cleared naturally. This is because the test only shows that the person has been exposed to H. pylori at some point in their life [ 1 ]. To diagnose an active H. pylori infection, other tests are more appropriate, such as:
- The urea breath test
- Stool antigen test
- Endoscopic biopsy with rapid urease testing These tests detect the actual presence of the bacteria rather than just the immune response to past exposure [ 1 ].
If a patient has a positive antibody test and symptoms suggesting H. pylori infection (like dyspepsia, abdominal pain, or symptoms of peptic ulcer disease), one of these active infection tests should be performed before initiating treatment [ 1 ]. This distinction is important because treating based solely on antibody positivity could lead to unnecessary antibiotic use in patients who don't have an active infection. The urea breath test, for example, has a sensitivity and specificity of more than 90% for active infection [ 1 ].
It's also important to note that certain medications, such as antibiotics, bismuth, and proton pump inhibitors (PPIs), can affect the accuracy of these tests, and patients should be off these medications for a certain period before testing [ 1 ]. In summary, a positive serum H. pylori antibody test should not be relied upon alone to diagnose an active infection, and further testing should be performed to confirm the presence of the bacteria before initiating treatment.
From the Research
Diagnostic Tests for Helicobacter pylori Infection
- The accuracy of diagnostic tests for Helicobacter pylori infection, including serum antibody tests and stool antigen tests, has been evaluated in various studies 2, 3, 4, 5, 6.
- A positive serum Helicobacter pylori antibody test may not necessarily indicate active infection, as it can also detect past infections 3, 6.
Serum Antibody Tests
- Serum Helicobacter pylori IgG antibody tests have been shown to have a sensitivity of 50% and specificity of 54% in one study 5.
- Another study found that 78.5% of patients with confirmed H. pylori infection tested positive for serum H. pylori IgG antibody, while 40.5% of patients exhibited positivity for both serum H. pylori IgG antibody and stool antigen test, indicative of active chronic infections 3.
Stool Antigen Tests
- Stool antigen tests have been shown to have high sensitivity and specificity, with one study reporting a sensitivity of 96% and specificity of 83% 5.
- Another study found that a novel stool antigen test had a sensitivity of 97% and specificity of 94% in detecting H. pylori infection 2.
- A prospective cohort study found that a newly developed stool antigen test had a sensitivity of 97.3% and specificity of 99.3% in detecting H. pylori infection 4.
Interpretation of Test Results
- A single positive noninvasive test in populations of low prevalence is most likely a false-positive result, and confirmation using a test that measures a different parameter is recommended 6.
- The results of multiple tests, including serum antibody tests and stool antigen tests, should be considered when interpreting the results of diagnostic tests for H. pylori infection 3, 5.