Helicobacter Pylori Antigen
Lihue Barken
In the pretreatment setting, positive results indicate infection with H pylori, and negative results indicate lack of infection. In the posttreatment setting, negative results indicate eradication if testing is performed at least 4 weeks after therapy is stopped. Positive results indicate treatment failure. Equivocal results with the polyclonal EIA test indicate that the optical density detected falls between positive and negative cutoff values, and the test likely needs to be repeated. [1]
H pylori antigen is a protein constituent of the H pylori bacterium, which is shed in human stool. This bacterium finds its way into the body via oral-to-oral or fecal-to-oral transmission, typically in childhood. Risk factors include an infected sibling and poor living conditions. [3] The bacteria start in the gastric antrum, where they are most abundant, and move proximally. [4] Most of the bacteria invade the mucous layer, but approximately 20% attach to the gastric epithelium via outer membrane proteins. [5]
H pylori has multiple factors that promote its survival, including flagella that help it to move into the mucous layer despite gastric peristalsis. It also produces urease, which helps it survive the acidic environment by neutralizing acid and modifying the mucosal viscosity. [5] The bacterium can also lie dormant in the coccoid form, which improves its survival. [4] These factors allow H pylori to persist indefinitely.
While pangastritis is affiliated with gastric ulcers and cancer, antral-predominant gastritis is associated with duodenal ulcers. It is not fully understood how H pylori causes duodenal ulcers, but the organism is linked to 80% of duodenal ulceration. It is believed that H pylori induces these ulcers by suppressing D-cell production of somatostatin, which leads to increased gastrin levels and thus greater acidity. This leads to metaplasia in the duodenum, allowing H pylori to colonize the duodenum and cause inflammation and ulceration. [7]
H pylori is believed to infect about half of the total world population and about 35% of the population in the United States. It is most notably known to cause of PUD, gastric adenocarcinoma, and MALT lymphoma. [6] Thus, H pylori antigen testing has strong implications. It is approved for use in the diagnosis of H pylori infection and to determine eradication of infection after therapy is completed.
H pylori stool antigen testing is newer than its noninvasive constituents, serology and the urea breath test. Stool antigen testing has a similar application to urea breath testing, which was previously the noninvasive test of choice after therapy to establish eradication. Serology cannot be used because it detects antibody titers, which can persist long after successful therapy. [9]
All 3 tests are approved for use in diagnosing infection. The advantages of stool antigen testing include its ease, rapid results, cost effectiveness, and easy storage. The test requires only one sample and can be performed easily at home. New rapid in-office tests are being manufactured that can be read in less than 10 minutes, facilitating immediate treatment. [1]
Chronic gastritis is typically asymptomatic unless it leads to complications, such as PUD, carcinoma, or MALT lymphoma. [6] Early detection of H pylori and verification of treatment success are important to preventing complications. For instance, upon H pylori eradication, MALT lymphoma completely resolves in over 80% of cases. [5] However, it is unclear if infection elimination can decrease the risk of gastric lymphoma and adenocarcinoma. [8]
Noninvasive testing makes clinical and economic sense in the setting of symptomatic disease if the patient is young and symptoms are vague. Alarming symptoms, such as weight loss, bleeding, or dysphagia, and older age at onset, are more suggestive of malignancy. In this case, invasive testing with endoscopy and biopsy is indicated. Invasive testing may also be necessary upon treatment failure to attain antibiotic sensitivities via culture. [12]
Investigation has revealed that H pylori stool antigen testing has particular implications for certain populations and circumstances. Cutoff values for EIA testing are set by manufacturers; however, studies show that the use of receiver operating characteristic (ROC) curve to set cutoffs yields more accurate results. Testing with ROC may help improve sensitivity and specificity in certain populations. Non-Western patients with higher-fiber diets and children younger than 5 years are two groups in whom testing is less sensitive and ROC may be beneficial. Results appear to be accurate in patients who have undergone partial gastrectomy and patients with end-stage renal disease (ESRD), but the test may not be appropriate in patients with cirrhosis. [1]
Although ROC may help improve sensitivity and specificity, there are certain circumstances in which false-positive and false-negative results appear to occur consistently. For instance, results are falsely positive in patients with gastrointestinal bleeding in some studies. [1] False-negative results have been shown to occur if, before testing, antibiotics or bismuth are used within 4 weeks or proton pump inhibitors are used within 2 weeks. [7] H pylori antigen testing appears to be more accurate at detecting eradication when performed 4-8 weeks posttreatment. [1]
Alexandra J Baumann, DO Resident Physician, Department of Internal Medicine, Albert Einstein Medical Center
Alexandra J Baumann, DO is a member of the following medical societies: American College of Physicians, American Osteopathic Association
Disclosure: Nothing to disclose.
Philip O Katz, MD, FACP, FACG Chairman, Division of Gastroenterology, Albert Einstein Medical Center; Clinical Professor of Medicine, Jefferson Medical College of Thomas Jefferson University
Philip O Katz, MD, FACP, FACG is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, American Society for Gastrointestinal Endoscopy
Disclosure: Serve(d) as a speaker or a member of a speakers bureau for: Medtronic
Received income in an amount equal to or greater than $250 from: Torax medical: pfizer consumer, .
H. pylori is a gram-negative, microaerophilic bacterium that can infect humans. It is often found in the stomach of affected individuals and causes inflammation and ulceration. Patients harboring the bacteria are asymptomatic with abdominal pain, nausea, vomiting, and dyspepsia developing only after gastritis and peptic ulcer disease have set in. This activity describes the evaluation and treatment of H. pylori and explains the role of the interprofessional team in managing patients with these conditions.
Objectives:
- Identify the pathophysiology of Helicobacter pylori infection.Summarize the use of a urea breath test in the evaluation of Helicobacter pylori infection.Describe the triple therapy used in the eradication of Helicobacter pylori infection.Outline the importance of collaboration and communication among the interprofessional team members to enhance the delivery of care for patients affected by Helicobacter pylori infections.
Helicobacter pylori (H. pylori) is a gram-negative spiral-shaped bacterium that affects up to 50% of the population worldwide, with a higher prevalence in developing countries.[1][2][3] H. pylori is the most important cause for chronic or atrophic gastritis, peptic ulcer, gastric lymphoma, and gastric carcinoma[4]; however, these complications are less often seen in children and adolescents compared to adults.[5] H. pylori infection is usually acquired in early childhood and persists in the absence of treatment.[6] A phase 3 clinical trial in children in China documented the efficacy and safety of an oral recombinant H. pylori vaccine, a future option to reduce the incidence of H. pylori infection.[7]
Prevalence of H. pylori varies across the world, with the United States having 5% prevalence in children less than 10 years.[1] The Hispanic and African American populations have a higher prevalence compared to White Americans.[9]
There are four important components that lead to the formation of clinical diseases such as gastritis and ulcer in H. pylori infection. First, the urease activity of H. pylori plays an important role in countering the acidic environment of the stomach. Second, the flagella-mediated motility helps H. pylori bacterium move towards the host gastric epithelial cells. This is followed by the bacterial adhesins interacting with the host cell receptors, leading to successful colonization and persistent infection. Finally, there are many effector proteins/toxins that include cytotoxin-associated gene A (Cag A) and vacuolating cytotoxin A (VacA) released by H. pylori that lead to host tissue damage. Both acute and chronic inflammation is seen in H. pylori gastritis as eosinophils, neutrophils, mast cells, and dendritic cells are stimulated.[9] The gastric epithelial layer also secretes chemokines to initiate innate immunity and activates neutrophils that further damages the host tissue leading to the formation of gastritis and ulcer.[10]
Microscopic gastric inflammation is always seen in H. pylori infection.[5] Hematoxylin and eosin (H&E) staining for visualizing the bacteria has a sensitivity and specificity up to 90%. Special stains like modified Giemsa stain, Warthin-Starry silver stain, Genta stain, and immunohistochemical (IHC) stain have shown to improve the specificity up to 100%.[11] H&E staining is normally sufficient for visualizing H. pylori while Giemsa stain is more beneficial compared to other stains as it is simple and consistent. In the presence of inflammation on histology and absence of bacteria on H&E or Giemsa staining, specialized IHC stains may be more useful. [12]
The majority of children with H. pylori infection are asymptomatic.[5] Symptoms, if present, are usually of gastritis or peptic ulcer disease such as abdominal pain, nausea, vomiting or dyspepsia. Children with these gastrointestinal symptoms should be investigated to identify the underlying etiology of the symptoms.[1] There are various extra-intestinal manifestations that are associated with H. pylori infection such as iron deficiency anemia and chronic immune thrombocytopenia (cITP). Therefore, guidelines recommend that non-invasive testing for H. pylori can be considered in children with cITP or with refractory iron deficiency anemia without an identifiable cause. Children may also be anemic as it has been documented that those infected with H. pylori have lower iron stores. There seems to be a poor association with other extra-intestinal manifestations such as otitis media, upper respiratory symptoms, periodontal disease, sudden infant death syndrome (SIDS), or short stature; therefore H. pylori testing is not recommended in such cases.[13]
d3342ee215