Dual-focus with narrow-band imaging (DF-NBI) is a novel technique to improve the quality of images of the irregular mucosal structures and microvessels of gastric neoplasms. The investigators compare this technique with conventional white light (WL) endoscopy to predict Helicobacter pylori infection.

The subjects are patients who underwent upper gastrointestinal endoscopy under sedation. Participants are randomized into DF-NBI and WL groups. Rapid urease test will be performed in all cases. By captured images of gastric mucosa, classification of DF-NBI for Helicobacter pylori infected mucosa will be developed and validated. The established classification of WL for Helicobacter pylori infection will be used. Finally, the investigators will compare the accuracy between two groups based on each classification.

Inclusion Criteria:

• consecutive patients who have undergone uper gastrointestinal endoscopy for diagnosis or screening of cancer.

Exclusion Criteria:

• Those whose Hp status had already been clarified
• Pregnancy
• History of partial gastrectomy
• Taking proton pump inhibitor, antithrombotics or antibiotics within 4 weeks

If needed, IPD will be shared.