Inclusion Criteria:
* Inclusion criteria for the AIG group:
1. Age range: 18-65 years old, without gender limitation;
2. Patients diagnosed with AIG: Previous gastroscopy (or) histological findings consistent with AIG, and serological tests support the diagnosis of AIG;
3. Previous colonoscopy or intestinal CT have ruled out inflammatory bowel disease, malignant tumors, history of pseudo and mechanical bowel obstruction, and there is currently no evidence to support these diseases;
4. At least 2 weeks without taking PPI/P-CAB;
5. Possessing the ability to independently or with the assistance of medical staff, complete hydrogen and methane breath tests and related questionnaire scoring;
6. Capable of completing the signing of informed consent forms as required.
Inclusion criteria for the acid suppression group:
1. Age: 18-65 years old, without gender limitation;
2. Patients who are non-AIG and need long-term acid inhibitor (PPI more than 8 weeks or P-CAB more than 4 weeks) due to gastroesophageal reflux and other reasons;
3. Patients with a 1-year history of gastroscopy, with no degree of microscopic atrophy, or with mild gastric mucosal atrophy (C-I and C-II according to the Kimura-Takemoto classification);
4. Previous colonoscopy or intestinal CT have ruled out inflammatory bowel disease, malignant tumors, history of pseudo and mechanical bowel obstruction, and there is currently no evidence to support these diseases;
5. Possessing the ability to independently or with the assistance of medical staff, complete hydrogen and methane breath tests and related questionnaire scoring;
6. Capable of completing the signing of informed consent forms as required.
Inclusion criteria for the control group:
1. Age: 18-65 years old, without gender limitation;
2. Patients with a 1-year history of gastroscopy, with no degree of microscopic atrophy, or with mild gastric mucosal atrophy (C-I and C-II according to the Kimura-Takemoto classification);
4\) Previous colonoscopy or intestinal CT have ruled out inflammatory bowel disease, malignant tumors, history of pseudo and mechanical bowel obstruction, and there is currently no evidence to support these diseases; 4) At least 2 weeks without taking PPI/P-CAB; 5) Possessing the ability to independently or with the assistance of medical staff, complete hydrogen and methane breath tests and related questionnaire scoring; 6) Capable of completing the signing of informed consent forms as required.
Exclusion Criteria:
* 1)Gastrointestinal endoscopy suggests patients with active gastrointestinal ulcers; 2)History of malignant tumors of the digestive system (not limited to the digestive tract), inflammatory bowel disease, and pseudo or mechanical bowel obstruction in the past; 3)Previous gastrointestinal resection surgery;appendectomy and cholecystectomy within 1 year; 4)History of gastrointestinal perforation, gastrointestinal bleeding, cholangitis, and acute or chronic pancreatitis within one year; 5)Evidence suggests current gastrointestinal infections (Helicobacter pylori, acute infectious enteritis); 6)History of type I diabetes and primary hypothyroidism (the patients with normal thyroid function can be included); 7)Diagnosed lactose malabsorption, lactose intolerance, and pancreatic exocrine dysfunction; 8)History of antibiotic use within four weeks; 9)History of endoscopic examination within two weeks; 10)History of taking gastrointestinal motility promoting drugs, probiotics, and laxatives within one week; 11)On the day before the test, consume fermentable foods such as yogurt, kimchi, soy sauce, oats, beer, etc; 12)Eight hours prior to testing, without fasting; 13)Smoking and vigorous exercise two hours before and during the testing period; 14)Difficulty in exhaling due to respiratory system diseases, or inability to fast or drink for extended periods of time, resulting in inability to complete hydrogen and methane breath tests; 15)Pregnant, lactating women, or those with poor overall compliance, or other situations that researchers consider necessary to exclude.
