The carbon 13 breath test has a positive reference value of greater than 4. The carbon 13 breath test is a way to detect the number of H. pylori infections in the body using the C-13 isotope as a marker, and the test procedure involves the subject remaining fasted for more than 3 hours, performing breath collection in a special collection bag, and performing complete closure. The test meal containing the C13 marker is then taken, and the patient sits and waits for about 20 minutes before the normal breath is collected using the brand new collection bag, which is immediately closed. The medical staff will put the two bags of gas samples into the breathalyzer for analysis and comparison. If the test result value is greater than 4, it means that the patient appears to have a positive H. pylori. The carbon 13 breath test method is easy to operate, highly accurate and safe in the process.