Various diagnostic assays for the detection of an H. pylori infection are available. Histological detection and culturing of the pathogen are gold standard, which require invasive gastroduodenoscopy to obtain gastric biopsy specimens. In the last decade, noninvasive approaches, such as serological detections, the [13C] and [14C]urea breath test (UBT), and detection H. pylori antigen or DNA in feces, helped and improved the evaluation of H. pylori infection status in patients.
H. Pylori Diagnosis
Because of low sensitivities of most serological assays for younger than 12 years of age patients, they are not suitable for pediatric. The UBT is a well-established noninvasive diagnostic assay and gives excellent performance for both adults and children, but its specificity decreases for infants and young children and need. In addition, the performance of UBT with infants and young children requires trained staff for air sampling with a face mask, and the test also requires expensive instruments, such as an isotope ratio mass spectrometer or an infrared isotope ratio spectrometer. Enzyme immunoassays (EIAs) for the identification of H. pylori antigens in fecal specimens circumvent these difficulties. EIAs based on monoclonal antibodies have shown consistent excellent results, with very high sensitivities and specificities for both adults and children. A major disadvantage of all the noninvasive tests described above is their inability to provide information on the susceptibility or resistance of H. pylori to antibiotics.
Noninvasive testing for H. Pylori Diagnosis
Although serologic tests are easily obtained and widely available, most clinical guidelines no longer endorse their use for testing for H pylori infection because they are less accurate than other noninvasive tests that measure active infection. Laboratory-based quantitative serologic ELISA tests have an overall accuracy of only 80%. In comparison, the fecal antigen immunoassay and [13C] urea breath test have excellent sensitivity and specificity (> 95%) at a cost of < $60. Although more expensive and cumbersome to perform, these tests of active infection are more cost-effective in most clinical settings because they reduce unnecessary treatment for patients without active infection. Recent proton pump inhibitors or antibiotics significantly reduce the sensitivity of urea breath tests and fecal antigen assays (but not serologic tests). Prior to testing, proton pump inhibitors should be discontinued 7–14 days and antibiotics for at least 28 days.
Endoscopic testing for H. Pylori Diagnosis
Endoscopy is not indicated to diagnose H pylori infection in most circumstances. However, when it is performed for another reason, gastric biopsy specimens can be obtained for detection of H pylori and tested for active infection by urease production. This simple, inexpensive ($10) test has excellent sensitivity (90%) and specificity (95%). In patients with active upper gastrointestinal bleeding or patients recently taking proton pump inhibitors or antibiotics, histologic assessment for H pylori is preferred. Histologic assessment of biopsies from the gastric antrum and body is more definitive but more expensive ($150–$250) than a rapid urease test. Histologic assessment is also indicated in patients with suspected MALTomas and, possibly, in patients with suspected infection whose rapid urease test is negative. However, serologic testing is the most cost-effective means of confirming H pylori infection in patients with a negative rapid urease test.