In 1994 the National Institutes of Health Consensus Development Conference concluded that Helicobacter pylori (H. pylori) infection is the major cause of peptic ulcer disease, present in 90% of patients with duodenal ulcer and 80% of gastric ulcers. Worldwide, the prevalence of H. pylori infection is estimated at 50%. The primary mode of transmission appears to be fecal-oral. In the United States the overall prevalence is 30-40%, with lower prevalence in younger age groups.
Immediately following infection, H. pylori causes acute gastritis. Some individuals spontaneously clear H. pylori, but most develop persistent infection, which leads to chronic active gastritis. Subsequent complications include gastric and duodenal ulcers, gastric lymphoma, and gastric adenocarcinoma. An estimated 16% of infected individuals in the U.S. develop duodenal ulcers. Infection in early childhood increases risk for later development of gastric adenocarcinoma. Fewer than 5% of infected individuals develop gastric lymphoma.
H. pylori infection may be diagnosed by invasive (endoscopy) or noninvasive methods. Complications including GI bleeding, weight loss, older age, or persistence of symptoms after antimicrobial therapy are indications for endoscopy. From endoscopy, the organism may be identified by culture, biopsy, or rapid urease testing (e.g. CLOtest).
Noninvasive testing includes serology, fecal antigen testing and urea breath testing.
- Enzyme immunoassay (EIA) for IgG antibody to H. pylori is the serologic method of choice for screening patients with uncomplicated dyspepsia. Serum IgG EIA have 90-95% sensitivity and 80-90% specificity. It should be noted that serum IgG assays have markedly reduced sensitivities in HIV-infected patients. Limitations of the test include possible inability to monitor therapy due to a slow decline in antibody levels. A positive result may only indicate exposure to the organism and does not necessarily correlate with active infection. Screening of asymptomatic individuals is not recommended due to the high prevalence of carriers in the general population, especially in the elderly.
- Several rapid immunoassays have been developed that produce a qualitative result in 4-10 minutes. Compared with serum EIA, these whole blood rapid immunoassays have reduced sensitivities (80-90%), but comparable specificities.
- The noninvasive urea breath test (UBT) has excellent sensitivity and specificity for the diagnosis and assessment of patients post therapy (both exceeding 95%) when compared to invasive methods. However, due to high cost, this testing is not recommended for routine screening in uncomplicated, untreated patients. UBT is useful in follow-up of patients who continue to be symptomatic despite antimicrobial therapy, and may confirm eradication of H. pylori within six weeks after therapy compared with a 6 to 12 month follow-up period with serology for IgG antibody.
- The newest FDA-approved noninvasive test is an EIA for detection of H. pylori antigen in stool specimens. Compared to other direct detection tests, the stool antigen test has a sensitivity of 93-98% with specificity of 88-96%. Because the test measures H. pylori antigen it may also be useful in confirming eradication shortly after therapy. Use of antimicrobials, proton pump inhibitors, and bismuth preparations prior to testing may cause false negative results.
The antigen test requires a fresh stool specimen submitted in an airtight container and refrigerated prior to transport. Stool in transport media, swabs or a preservative is not appropriate. Specimen requirement for IgG antibody is one SST tube of blood. Blood collected in a lavender top (EDTA) or light blue top (sodium citrate) tube is also acceptable.
Results are reported as negative or positive. The reference value is negative.
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