Diagnostic tests for an H. pylori infection can be invasive or noninvasive. Noninvasive testing is more cost-effective, particularly for low-risk patients.

By Laura Vivian, MS, HT(ASCP), QIHC; M. Aamir Ali, MD; and Laura Reid      

Helicobacter pylori (H. pylori) is one of the world’s most common bacterial infections with a global prevalence of approximately 50%. Prevalence is inversely correlated with socioeconomic status with significant variation across regions. For example, the prevalence of H. pylori infection is 35.6% overall in the United States, and as high as 74% in the Alaskan Indigenous population1. Additionally, data shows that individuals with an H. pylori infection have a six times higher risk of developing gastric cancer.2 

H. pylori infection causes characteristic changes in the gastric lining, classified as chronic atrophic gastritis, in all infected individuals. H. pylori gastritis has been formally classified as an infectious disease and hence should be treated when diagnosed. 3,4  

Chronic atrophic gastritis contributes to the development of duodenal ulcers, gastric ulcers, and mucosa-associated lymphoid tissue (MALT) lymphoma. In addition, chronic atrophic gastritis can be the first step in a multi-step cascade that can ultimately lead to gastric cancer.3 As a result of the strong correlation between H. pylori infection and gastric cancers, the World Health Organization (WHO) has designated H. pylori to be a Class 1 (definite) carcinogen.5 Eradication of H. pylori infection prevents the occurrence and recurrence of gastric and duodenal ulcers and MALT lymphoma.

Indications for H. Pylori Infection Testing

Guidelines for patients in the United States and Canada, from the American College of Gastroenterology recommend H. pylori infection testing in individuals with active peptic ulcer disease, prior history of peptic ulcer disease without prior treatment for H. pylori, low-grade gastric MALT lymphoma, or a history of endoscopic resection of gastric cancer. Testing is also recommended in individuals with dyspepsia, or upper abdominal discomfort, who are younger than age 60 and have no alarm signs that raise concern for underlying gastric cancer (weight loss, vomiting, anemia).6

Once a patient has one or more indications for testing, the appropriate testing modality should be determined. Diagnostic tests for H. pylori infection can be categorized as invasive (endoscopy, biopsy) or noninvasive (serology, urea breath test, and stool antigen test). Noninvasive testing is more cost-effective in individuals at low risk for underlying malignancy and is the test of choice in the evaluation of dyspepsia in patients without alarm signs who are younger than age 60.6

Additionally, guidelines for H. pylori diagnosis support tests of active infection, as opposed to tests that demonstrate prior exposure, such as serology, as the latter remain positive even after the infection has been eradicated, thereby prompting unnecessary use of antibiotics.7

A Review: H. Pylori Diagnostic Tests

Invasive Testing: Biopsy Based Rapid Urease Test & Histology

During endoscopy, biopsies are taken from the upper gastrointestinal tract. The biopsy sample may undergo a series of tests including culture, staining, microscopy, or rapid urease testing. These methods require experienced specialists and may take several days to obtain results.

Rapid urease tests (RUT) consist of a urea test reagent and a medium to detect ammonia production. The sensitivity for RUT and histology can be lowered significantly in the setting of active gastrointestinal bleeding, proton pump inhibitor use, partial gastrectomy, or single biopsy specimens from one region of the stomach. Multiple biopsies spanning different regions of the stomach are recommended to optimize diagnostic yield.8,9

Histology with microscopic identification of H. pylori organisms is considered the reference standard for the diagnosis of H. pylori infection. To avoid false negative results, proton pump inhibitors should be discontinued one to two weeks before biopsy, and at least two specimens each should be obtained from the antrum and corpus.9 Histology is unlikely to be used for the confirmation of eradication in H. pylori-positive individuals due to the invasive nature of the test.

Noninvasive testing:  Serology, Urea Breath, and Stool Antigen

Noninvasive testing consists of urea breath testing (UBT), stool antigen testing, and serology. A major distinction within this category is that UBT and stool antigen tests are tests of active infection, and serology is a test of prior exposure.

Serology (antibody)

Since H. pylori is a chronic infection, ELISA-based testing of IgG antibodies against bacterial antigens has long been the mainstay of diagnosis. While serology is inexpensive and easy to perform, it suffers from significant limitations and is no longer recommended by ACG guidelines for the diagnosis of H. pylori infection. The most significant limitation is that serology is a test of prior exposure as opposed to active infection; individuals with prior exposure to H. pylori who are no longer infected may test positive for months or years after the resolution of infection.7 Serology cannot confirm successful treatment or the eradication of H. pylori. The use of serology can lead to overtreatment of patients who do not actually have an H. pylori infection; another contributing factor to antibiotic resistance.

Commercially available serologic tests for the detection of H. pylori have sensitivity and specificity of 85% and 75% and are significantly less accurate than stool antigen tests and UBT.10 A further shortcoming of serology is its low positive predictive value. In most of the United States, the positive predictive value of serology is approximately 50%, which means that half the positive serologic tests are false positives.

Urea Breath Test

UBT, a noninvasive test for active H. pylori infection, leverages the production of urease by H. pylori organisms. The patient provides a pre-ingestion breath sample, consumes a drink solution containing either 13C or 14C labeled urea, then provides a post-ingestion breath sample. 14C labeled urea is a radioactive isotope whereas 13C is non-radioactive. While the dose of radiation in 14C is low, it should not be used in children, pregnant women, and women of childbearing age. 13C-based UBT is the test of choice. If H. pylori infection is present, bacterial urease hydrolyzes the urea to release labeled carbon dioxide, which diffuses into the blood and is expelled by the lungs, where it can be detected in breath samples. Breath samples may be collected 15 minutes after ingestion of urea, which makes the test convenient and easy to administer in a clinic, office, or lab.11

UBT is highly sensitive and specific, with a meta-analysis of 23 studies showing a sensitivity of 96% and a specificity of 93%.12 The American College of Gastroenterology (ACG) clinical practice guidelines recommend UBT for the diagnosis of H. pylori infection. A Cochrane database review compared the non-invasive tests for detection of H. pylori indirectly (as there are few head-to-head studies) and found UBT to have greater diagnostic accuracy than the stool antigen test or serology.13 In addition, patients prefer providing a breath sample over a stool sample. In a study of patient acceptability of available non-invasive tests of active infection, 58% of patients preferred UBT, whereas 34% preferred a stool antigen test.14

Stool antigen test

The stool antigen test, like UBT, is supported by the ACG guidelines for the detection of active H. pylori infection and confirmation of eradication after antibiotic treatment.15 Specimen collection is easy for patients as it can be done from the comfort of their home. Stool antigen tests detect the presence of H. pylori bacterial antigens in stool samples using polyclonal or monoclonal antibodies. Due to the low accuracy of polyclonal antibodies, particularly in patients being tested for eradication of infection after antibiotic therapy, polyclonal stool antigen tests have been largely replaced by the more specific EIAs utilizing monoclonal antibodies.

A meta-analysis of 22 studies showed the sensitivity and specificity of the monoclonal antibody-based stool antigen tests to be 94% and 97%, respectively, in patients who had not undergone treatment for infection. The same meta-analysis pooled data from 12 studies in patients undergoing monoclonal antibody-based stool antigen testing to confirm eradication of infection; sensitivity and specificity remained high at 93% and 96%, respectively. In eight post-treatment studies, the monoclonal technique showed a higher sensitivity at 91% compared to the polyclonal technique at 76% 16

H. Pylori Infection Testing Critical for Patient Management

Accurately diagnosing and treating H. pylori infection is essential for appropriate patient management, preventing long-term health complications, and ensuring effective antibiotic use. Choosing the right diagnostic test for H. pylori infection may vary depending on the clinical scenario, patient factors, and healthcare provider preferences. Patient compliance can also vary depending on convenience, invasiveness, and patient preferences.

UBT and stool antigen tests are recommended by clinical guidelines for noninvasive active infection testing as they provide higher diagnostic accuracy compared to conventional serology testing. These tests can be easily integrated into routine clinical practice, and do not require specialized equipment or facilities compared to endoscopy procedures.

From the patient’s perspective, the convenience of being tested on the same day during a routine office visit improves patient satisfaction and more importantly, increases testing compliance. From the provider’s perspective, noninvasive active infection testing allows for simplified ordering, shorter turnaround time to result, greater control over specimens, and streamlining of the workflow process. These factors can ultimately improve diagnostic accuracy and clinical outcomes for patients.

About the Authors

Laura Vivian, MS, HT(ASCP), QIHC, is the executive Director of Capital Digestive Care Laboratories.

M. Aamir Ali, MD, is a gastroenterologist  at Capital Digestive Capital Digestive Care.

Laura Reid is a product manager at Meridian Bioscience Inc.


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