This is a multicenter, cross-sectional study. It is based on fecal methylation site detection, H. pylori susceptibility testing of fecal samples, and a combination of the two, compared with the "gold standard" imaging tests, CT, gastroscopy and/or pathology, for gastric cancer, benign diseases such as gastritis, and health check-ups.

Primary study objective: to evaluate the sensitivity and specificity of fecal methylation site-based and fecal Helicobacter pylori gastric cancer susceptibility gene assays applied to early diagnosis and screening of gastric cancer.

Secondary research objectives: 1. the accuracy, kappa value, area under the ROC curve, positive likelihood ratio, negative likelihood ratio, positive predictive value, and negative predictive value of fecal methylation site-based testing and fecal Helicobacter pylori gastric cancer susceptibility gene-based testing applied for predicting gastric cancer; 2. whether the predictive ability is significantly higher than that of conventional tumor markers, such as CA19-9, CEA, and CA72-4; and 3. the follow up of Gastritis and healthy people, to assess the cases of gastric cancer during the follow-up period and the clinical diagnosis and treatment prediction; 4. Follow-up gastric cancer patients, to assess the association with gastric cancer recurrence metastasis and treatment.

Inclusion Criteria:

• Age ≥ 18 years old, male or female not limited.
• Within 90 days, the gastroscopy and/or pathological results confirm the absence of gastric cancer.
• Patients must be able to fully understand the informed consent form and be able to personally sign it.

Exclusion Criteria:

• Severe cardiac, hepatic, or renal insufficiency, or psychiatric disorders.
• A previous history of malignant tumors of the upper gastrointestinal tract.
• Women during pregnancy.
• Those with undefined pathology.
• Those with unsatisfactory sample retention (e.g., too small a sample size)

The subjects of this clinical study are from the community population in the high incidence area of gastric cancer in Tongling. The subjects will collect feces during medical visits or physical examinations, and undergo fecal methylation DNA and Helicobacter pylori gastric cancer susceptibility gene testing. The researchers determine the study subjects based on the inclusion and exclusion criteria and inform them of the content of the informed consent form.