Enzyme Immunoassay for the Detection of H. pylori Antigen in Human Stool
Introduction
Helicobacter pylori (H. pylori) is a gram-negative, spiral-shaped bacterium that colonizes the gastric mucosa. Numerous studies have demonstrated a strong correlation between H. pylori infection and various gastrointestinal disorders, including chronic gastritis, peptic ulcers, duodenal ulcers, and gastric adenocarcinoma (Suerbaum & Michetti, 2002). The prevalence of H. pylori in patients with duodenal ulcers is approximately 95-98%, while 60-90% of gastric ulcer patients also harbor the infection (Malfertheiner et al., 2017).
Despite its high prevalence, many individuals (over 50% of those above the age of 50) are colonized by H. pylori without developing clinical symptoms (Chey et al., 2017). The presence of bacterial colonization alone does not confirm an active infection. Diagnostic confirmation requires the presence of clinical symptoms in conjunction with laboratory findings such as positive urea breath tests, serological assays, stool antigen tests, or histological examination via endoscopy (Gisbert & Calvet, 2011).
Diagnostic methods for H. pylori infection include invasive and non-invasive approaches. The invasive method requires endoscopy with biopsy, followed by histopathological examination or rapid urease testing. While highly accurate, these methods are costly and uncomfortable for patients. Non-invasive tests, including the urea breath test (UBT), serologic assays, and stool antigen tests, provide effective alternatives. The detection of H. pylori antigens in stool samples is a reliable indicator of active bacterial colonization in the gastrointestinal tract, with enzyme-linked immunosorbent assay (ELISA) being the preferred method for stool antigen detection (Vaira et al., 2002).
Clinical Significance
Accurate diagnosis and monitoring of H. pylori infection are essential for preventing long-term complications. Untreated infections can lead to chronic gastritis, gastric and duodenal ulcers, and an increased risk of gastric malignancies (Wroblewski et al., 2010). ELISA-based stool antigen tests are particularly useful in both initial diagnosis and post-treatment monitoring due to their high sensitivity and specificity (Gisbert & Calvet, 2011). The test is especially beneficial for pediatric and geriatric patients, where endoscopic procedures may be impractical.
Test Principle
The Helicobacter pylori Stool Antigen ELISA Kit employs a sandwich enzyme-linked immunosorbent assay (ELISA) technique. The method utilizes monoclonal antibodies coated on microtiter wells to capture H. pylori antigens from stool specimens. The antigen-antibody complexes are then detected using a secondary antibody conjugated with horseradish peroxidase (HRP). The addition of a chromogenic substrate leads to a colorimetric reaction proportional to the antigen concentration in the sample. The reaction is halted using a stop solution, and optical density (OD) is measured at 450 nm using an ELISA reader.
References
- Chey, W. D., Leontiadis, G. I., Howden, C. W., & Moss, S. F. (2017). ACG clinical guideline: Treatment of Helicobacter pylori infection. The American Journal of Gastroenterology, 112(2), 212-239.
- Gisbert, J. P., & Calvet, X. (2011). Review article: Helicobacter pylori ‘test-and-treat’ strategy for management of dyspepsia. Alimentary Pharmacology & Therapeutics, 34(5), 545-556.
- Malfertheiner, P., Megraud, F., O’Morain, C. A., Gisbert, J. P., Kuipers, E. J., Axon, A. T., … & Hunt, R. (2017). Management of Helicobacter pylori infection—the Maastricht V/Florence consensus report. Gut, 66(1), 6-30.
- Suerbaum, S., & Michetti, P. (2002). Helicobacter pylori infection. New England Journal of Medicine, 347(15), 1175-1186.
- Vaira, D., Malfertheiner, P., Megraud, F., Axon, A. T., Deltenre, M., Hirschl, A. M., … & Tytgat, G. N. (2002). Diagnosis of Helicobacter pylori infection with a new non-invasive antigen-based assay. The Lancet, 357(9252), 1618-1623.