Indications for Testing
Testing is used to diagnose H. pylori infection and evaluate treatment success. Screening asymptomatic patients in the general population is not recommended.
The decision to use noninvasive or invasive test methods for diagnosis of H. pylori infection is dependent on the age of the patient and whether the patient presents with alarm symptoms (gastrointestinal bleeding, unexplained iron deficiency anemia, early satiety, unexplained weight loss, progressive dysphagia, odynophagia, recurrent vomiting, family history of gastrointestinal cancer, and previous esophagogastric malignancy). Noninvasive testing using either the urea breath test or the stool antigen test is indicated for adults younger than 60 years of age who present without alarm symptoms. Invasive testing methods involving endoscopy and biopsy are indicated for children, adults who are 60 years or older, and those who present with alarm symptoms. Noninvasive testing may be acceptable for children when evaluating causes of chronic immune thrombocytopenic purpura or when a false-negative invasive test result is suspected. For accurate results, it is recommended that patients stop use of proton-pump inhibitors (PPIs) for 2 weeks before any H. pylori testing. Histamine 2-receptor antagonists may reduce urease activity on urea breath tests and should be discontinued 24-48 hours before the sample is collected.
Urea Breath Test
The 13C-urea breath test is considered the best noninvasive approach for the diagnosis of active H. pylori infection. Testing requires the patient to fast and abstain from smoking for 1 hour before testing. Achlorhydria or urease-positive organisms other than H. pylori in the gut may increase the risk of a false-positive result.
The stool antigen test uses an enzyme immunoassay to detect H. pylori antigen in stool. Its ability to detect infection is equal to that of the urea breath test.
Invasive testing strategies require upper endoscopy with biopsy. Biopsy of the antrum is recommended at a minimum, but biopsy of additional areas (eg, the corpus) may improve diagnostic utility and is recommended in children. Biopsy-based tests are less sensitive when performed during active gastrointestinal bleeding; if a false-negative result is suspected, noninvasive testing may be considered.
When endoscopy is indicated and there is no contraindication for biopsy, the rapid urease test is recommended as a first-line diagnostic test ; it is accurate and inexpensive and allows for immediate treatment. The rapid urease test is highly sensitive but not always specific for H. pylori, as other urease-positive organisms in the gut may cause a false-positive result. Additionally, because active gastrointestinal bleeding decreases the sensitivity of urease-based tests, histology may be preferable. In patients who have not recently used PPIs and antibiotics, the rapid urease test may be preferred over histology.
Histology (With or Without Staining)
The sensitivity of histology in detecting H. pylori is subject to the area being sampled and the number of samples, but the addition of stains (eg, Giemsa, Warthin-Starry, hematoxylin and eosin, immunohistochemistry) may increase the sensitivity. Histologic evaluation has the added value of potentially uncovering an unsuspected pathology, such as inflammation, metaplasia, dysplasia, and malignant neoplasm. Although PPIs and antibiotics can interfere with bacterial density, histology is better for patients who have recently used these medications. In children, histology should be performed in addition to another biopsy-based test.
Although highly specific (100%), culture is less sensitive than either the rapid urease test or histology and has the disadvantage of requiring a 2-week incubation period that may or may not yield successfully growing colonies. However, it is recommended in children and can be used as the sole test for diagnosis in this patient group. An additional benefit of culture is that it enables antibiotic susceptibility testing.
Follow-up testing after treatment using either the urea breath test or stool antigen test is recommended in both children and adults. This should occur no sooner than 4 weeks after completion of antibiotic therapy and after PPI therapy has been suspended for 1-2 weeks. Biopsy-based testing may also be performed in adults when a repeat endoscopy is needed. Because all tests are highly sensitive and specific, the choice of which test to use can be based on patient needs and preferences. However, the rapid urease test is not recommended by some for evaluation of eradication after treatment.