Gastric String Test Combined With a Rapid Antigen Assay for Helicobacter Pylori Detection

Background and Rationale

Helicobacter pylori infection is a major cause of chronic gastritis, peptic ulcer disease, and gastric cancer. Commonly used non-invasive diagnostic methods include the ^13C-urea breath test (UBT) and stool antigen testing. Although these methods are widely used, stool-based testing requires specimen collection and handling, while UBT generally requires specialized analytical equipment.

A minimally invasive gastric string sampling device may provide an alternative approach for obtaining gastric specimens without conventional upper gastrointestinal endoscopy. Combining this sampling method with a rapid antigen assay may offer a convenient approach for H. pylori detection. However, the diagnostic performance of this combination using string-collected gastric mucus has not yet been established.

Study Design

This is a single-center, prospective, single-group pilot diagnostic accuracy study conducted at Fu Jen Catholic University Hospital, Taiwan.

An enriched enrollment strategy will be adopted to include 30 participants with positive UBT results and 10 participants with negative UBT results. All participants will undergo the same investigational procedure, and their previously obtained ^13C-UBT results will serve as the reference standard for diagnostic comparison.

Investigational Procedure

The investigational procedure combines two medical devices:

1. Disposable Gastric Specimen Collection String: A minimally invasive gastric sampling device distributed by POCT Biotech Co., Ltd. (CE-certified, CE No. 6976663940137), used to collect gastric mucus specimens.
2. Helicobacter pylori Rapid Antigen Test: A rapid antigen assay manufactured by Strong Biotech Co., Ltd. (Taiwan Food and Drug Administration Medical Device License No. 007277), used to detect H. pylori antigens in the collected specimens.

The use of string-collected gastric mucus with this rapid antigen assay represents an investigational application. Results obtained from this procedure will be used exclusively for research purposes and will not guide clinical diagnosis or treatment decisions.

Study Procedures

Participants will fast overnight before the study procedure. Each participant will swallow a disposable gastric specimen collection capsule with approximately 250 mL of water. After the capsule dissolves, the attached string will remain in the stomach for approximately 60 minutes to absorb gastric mucus.

The string will subsequently be retrieved by trained study personnel and immersed in the designated antigen extraction buffer. The extracted specimen will then be applied to the H. pylori rapid antigen test cassette, and the result will be interpreted after approximately 3-5 minutes.

In addition to qualitative interpretation, two independent investigators blinded to the participants' UBT results will assess the test-line (T-line) color intensity using a standardized reference chart, assigning a semi-quantitative score ranging from 0 to 4.

Safety Monitoring

Participant discomfort during capsule swallowing, gastric retention, and string retrieval will be evaluated using a Visual Analog Scale (VAS).

Potential procedure-related adverse events, including nausea, gagging, throat discomfort, mucosal irritation or injury, bleeding, and difficulty retrieving the string, will be monitored and documented. Clinically significant adverse events will be managed according to institutional clinical practice, and serious adverse events will be reported to the Institutional Review Board in accordance with applicable regulations.