Clarithromycin-based Triple Therapy for 14 Days Versus Sequential Therapy 10 Days in the First Line Therapy

Inclusion Criteria: * Patients are aged greater than 20 years who have H. pylori infection without prior eradication therapy and are willing to receive the sequential therapy will be eligible for enrollment. * Written informed consents will be obtained from all patients prior to enrollment. Exclusion Criteria: Patients will be excluded from the study if any one of the following criteria is present: * children and teenagers aged less than 20 years, * history of gastrectomy, * gastric malignancy, including adenocarcinoma and lymphoma, * previous allergic reaction to antibiotics (amoxicillin, clarithromycin, levofloxacin, metronidazole) and prompt pump inhibitors (lansoprazole), - contraindication to treatment drugs, * pregnant or lactating women, * severe concurrent disease * Patients who cannot give informed consent by himself or herself.