Helicobacter pylori (H. pylori) is a spiral-shaped bacterium that can colonize the human stomach and is implicated in most cases of chronic gastritis, gastric ulcers, and duodenal ulcers. This bacterium's ability to thrive in the acidic environment of the stomach is largely due to the enzyme urease, which it produces. Urease catalyzes the conversion of urea to ammonia and carbon dioxide, neutralizing stomach acids and allowing the bacterium to survive. Over the years, researchers have employed different methods to diagnose this infection. Common methods include non-invasive methods such as urea breath tests (UBT), serology and stool antigen detection. Alternatively, invasive techniques utilizing endoscopic gastric biopsy for histopathology and microbial identification tests including rapid urease test (RUT), bacterial culture and biochemical reactions can also be employed [1]. Among these methods, the 13C-urea breath test has emerged as a preferred diagnostic tool due to many advantages.
Fig. 1. Invasive and non-invasive diagnostic tools for Helicobacter pylori.
Basic Principles of the 13C-Urea Breath Test
The urea breath test is designed to detect active H. pylori infection by measuring the enzymatic activity of urease. In the 13C-urea breath test, the patient ingests urea labeled with a non-radioactive carbon isotope, carbon-13. In the presence of H. pylori, the urease enzyme breaks down the ingested urea into ammonia and 13C-labeled carbon dioxide. This carbon dioxide is absorbed into the bloodstream and ultimately exhaled through the lungs. The presence of elevated levels of 13C in the exhaled breath indicates a positive result for H. pylori infection.
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How the Test Works
- Preparation: The patient may be asked to avoid certain medications (like antibiotics, bismuth preparations, and proton pump inhibitors) for a specified period before the test. They may also need to fast for several hours prior to the test.
- Ingestion of Urea: The patient consumes a solution that contains urea labeled with a stable isotope of carbon, specifically carbon-13.
- Metabolism by H. pylori: If H. pylori are present in the stomach, it will metabolize the urea into ammonia and carbon dioxide. The carbon dioxide produced will contain the 13C isotope.
- Breath Sample Collection: After ingestion, breath samples are collected at specific intervals (usually within a few minutes to an hour). The exhaled breath is analyzed for the presence of 13C-labeled carbon dioxide.
- Measurement and Analysis: The patient's breath is then analyzed for the enriched carbon-13 isotope using precise instruments such as isotope ratio mass spectrometry or nondispersive infrared spectrometry. A higher level of 13C in the breath indicates the presence of H. pylori, as it reflects the bacteria's activity in metabolizing the urea.
Advantages of the 13C-Urea Breath Test
- Non-Invasiveness: Unlike endoscopic procedures, the 13C-urea breath test is non-invasive, making it a less daunting option for patients.
- High Accuracy: The test boasts high sensitivity and specificity, comparable to invasive diagnostic procedures. This ensures a low rate of false positives and negatives.
- Quick Results: The results are available quickly, often within minutes if analyzed in an office setting with appropriate equipment, making it convenient for both patients and healthcare providers.
- Safety and Suitability: Being non-radioactive, the 13C test is safe for a wide variety of patients, including children and pregnant women, eliminating the concerns associated with the carbon-14 alternative.
Clinical Relevance and Applications
Clinicians rely on the 13C-urea breath test not only for diagnosing H. pylori but also for monitoring treatment efficacy. As part of a comprehensive Helicobacter pylori management strategy, this test can guide therapeutic approaches, ensuring that eradication efforts are successful and minimizing the risks associated with persistent infections, such as gastric ulcers and gastric cancer. Moreover, the test's high sensitivity and specificity make it an indispensable tool in the follow-up of patients who have undergone treatment, providing reassurance to both clinicians and patients of the infection's resolution.
Reference
- Said Z. N. A. and El-Nasser A. M. Evaluation of urea breath test as a diagnostic tool for Helicobacter pylori infection in adult dyspeptic patients[J]. World Journal of Gastroenterology, 2024, 30(17): 2302.
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