What are the implications of a positive Helicobacter pylori (H. pylori) Immunoglobulin G (IgG) test result?

From the Guidelines

A positive H. pylori IgG blood test indicates you have been infected with Helicobacter pylori bacteria at some point, but doesn't necessarily mean you have an active infection, and therefore, further testing such as a stool antigen test, urea breath test, or endoscopy is recommended to confirm active infection. If you're experiencing symptoms like stomach pain, nausea, or heartburn, you should consult your doctor for further testing. Treatment typically involves triple or quadruple therapy for 10-14 days, combining antibiotics (such as amoxicillin, clarithromycin, metronidazole, or tetracycline) with a proton pump inhibitor (like omeprazole or lansoprazole) and sometimes bismuth subsalicylate, as suggested by the most recent guidelines 1. A specific regimen might include amoxicillin 1g twice daily, clarithromycin 500mg twice daily, and omeprazole 20mg twice daily for 14 days. After treatment, follow-up testing is recommended to confirm eradication. H. pylori can cause peptic ulcers and increase gastric cancer risk, so treating active infections is important to prevent these complications, as highlighted in a recent review 1. The bacteria damages the stomach's protective mucus layer, allowing stomach acid to irritate the sensitive lining beneath.

Some key points to consider when managing H. pylori infection include:

• The importance of confirming active infection before starting treatment, as serologic tests can remain positive long after the infection has been eradicated 1
• The use of non-invasive tests such as the urea breath test or stool antigen test to confirm active infection, which have high sensitivity and specificity 1
• The need for follow-up testing after treatment to confirm eradication, as treatment failure can occur due to antibiotic resistance 1
• The potential for antibiotic resistance to impact treatment efficacy, and the need for surveillance registries to monitor resistance patterns 1

Overall, the management of H. pylori infection requires a thoughtful and individualized approach, taking into account the patient's symptoms, test results, and medical history, as well as the potential risks and benefits of treatment, as emphasized in recent guidelines 1.

From the Research

H pylori Positive IgG

• The presence of H pylori positive IgG indicates that the individual has been exposed to the bacteria at some point in their life 2.
• However, it does not necessarily mean that the individual is currently infected, as IgG antibodies can remain in the system for a long time after the infection has been cleared 3, 2.
• The sensitivity of serum H pylori IgG is higher (0.94) than urea breath and stool antigen tests (0.64 and 0.61, respectively), making it a useful tool for initial diagnosis 2.
• The use of serology, including IgG testing, can be useful in combination with other non-invasive tests, such as urea breath test or stool antigen test, to define the H pylori status in some patients 4.
• In patients with atrophic body gastritis, neither urea breath test nor stool antigen test per se add useful information regarding active H pylori infection, but these non-invasive tests may be important in combination with histology and serology to define the H pylori status 4.

Diagnostic Tests for H pylori

• The urea breath test (UBT) and stool antigen test (SAT) are non-invasive tests that can be used to diagnose H pylori infection 5, 3, 6.
• The sensitivity and specificity of these tests can vary, with the stool antigen test showing high sensitivity (96%) and specificity (83%) in one study 3.
• The UBT has also been shown to be accurate, with a sensitivity of 89% and specificity of 73% in one study 3.
• However, the accuracy of these tests can be affected by various factors, such as the presence of atrophic body gastritis or the use of eradication therapy 6, 4.

Interpretation of Test Results

• A positive IgG result should be interpreted in combination with other test results, such as urea breath test or stool antigen test, to confirm the diagnosis of H pylori infection 2.
• A negative IgG result can be used to rule out H pylori infection, especially in low-prevalence populations 2.
• The use of reflexive testing with positive serology followed by either stool antigen or urea breath test may optimize diagnostic accuracy in low-prevalence populations 2.