To perform a prospective, observational, international, multicentre, in vivo study to assess the performance of regular arrangement of collecting venules (RAC) for the exclusion of Helicobacter pylori (Hp) infection using white light high definition (HD) endoscopy without any kind of zoom or magnification.

Gold standard will be mucosal biopsies (Sydney protocol) or urease test. Immunohistochemistry (IHC) should be performed in case of a negative histologic study for Hp in patients taking proton pump inhibitors (PPIs).

Participants will perform a training test with 20 pictures of the distal part of the lesser curvature before starting the inclusion of cases.

Secondary objectives are:

• To assess whether age, sex and PPIs, have an influence on the results of RAC.
• To assess the correlation of atrophic gastritis and intestinal metaplasia (confirmed in histopathological samples) and RAC.
• To assess reproducibility of RAC on real time examinations with different operators and in different countries with different Hp infection prevalence.

Primary and secondary variables

The primary study variable is:

- Endoscopic detection of RAC.

Secondary variables will be considered:

• Sex

• Age

• PPI intake in the last two weeks

• Centre

• Country

• Hp prevalence

• Endoscopist

• Type of endoscope

• Significant findings (need of histological confirmation)

  • Atrophic gastritis
  • Intestinal metaplasia
  • Erosive gastritis
  • Benign gastric ulcer
  • Gastric adenoma
  • Gastric cancer

This is a prospective, multicentre, international study without a control group.

Training phase Before starting the inclusion of patients, 20 HD images previously collected by the principal investigator will be sent to each of the study investigators. Pictures will clearly show the RAC pattern present or absent at the level of the distal gastric lesser curvature. In case of doubtful RAC, the pattern shall be considered negative. Investigators will be able to discuss their questions and doubts after the training phase (videoconference).

Endoscopic examination Upper endoscopy will be performed with HD endoscopes and a high-definition screen. Two endoscopists will participate in each hospital. The examination will be performed according to the protocol of each centre. Visualisation of the entire oesophageal, gastric and duodenal surface will be performed as in routine clinical practice. The presence of RAC will be assessed during the gastric exploration with sufficient insufflation and its detection will be considered as the presence of a regular starfish-shaped erythematous punctation in the lower part of the lesser curvature of the gastric body, close to the incisura angularis.

In case of the presence of residues in the gastric cavity that prevent the correct visualisation of the area, water washings shall be performed for the correct characterisation of the mucosa. At least one photo of the described gastric region shall be taken with the image processor system to maintain its high-definition quality. All the data (name, date of birth, clinical record number, date of exploration…) will be removed from the picture to ensure the anonymisation. Subsequently, the photographs will be downloaded and saved in a folder on a network drive of each hospital.

After characterisation of the gastric mucosa, the Hp infection status will be assessed by taking biopsies with a standard forceps for anatomopathological study according to Sydney's protocol (2 in the antrum, 1 in the incisura and 2 in the body). Ideally, biopsies for a urease test will also be obtained.

Histopathological examination Samples shall be fixed in formalin and analysed by the Anatomical Pathology service for histological examination by haematoxylin and eosin (H&E) and special staining for Hp (e.g. modified Giemsa). In patients taking PPI, if Hp is negative in the H&E histological study, the study will be completed by immunohistochemical (IHC) staining.

Inclusion Criteria:

• Patients older than 18 years without previous history of Hp infection or eradication undergoing a gastroscopy

Exclusion Criteria:

• Patients taking oral anticoagulants (acenocoumarol and new anticoagulants as dabigatran, rivaroxaban, apixaban and edoxaban), NSAIDs or with intake of antibiotics in the last 4 weeks, but aspirin at a dose of 100 mg per day will be included
• Diseases that affect the gastric mucosa and preclude the evaluation of the collecting venules pattern (portal hypertension, gastric lymphoma)
• History of previous gastric cancer or patients in surveillance for preneoplastic lesions (atrophic gastritis/IM),
• Previous gastric surgery,
• Active bleeding or presence of blood or food that would impede a complete mucosal evaluation.
• Negative to participate in the study or inability to provide signed consent

Patients older than 18 years without previous history of Hp infection or eradication undergoing a gastroscopy in each center