GastritisGastritis, AtrophicHelicobacter pyloriGastric MucosaHelicobacter InfectionsMetaplasiaChronic DiseaseStomach NeoplasmsPyloric AntrumStomach UlcerStomachPeptic UlcerPepsinogen AAchlorhydriaDyspepsiaGastroscopyDuodenitisDuodenal UlcerBiopsyPepsinogen CStomach DiseasesGastrinsHelicobacter heilmanniiBile RefluxHelicobacterGastric JuiceUreaseCampylobacterAtrophyHelicobacter felisPrecancerous ConditionsEndoscopy, GastrointestinalAntigens, BacterialGastritis, HypertrophicBacterial ProteinsLymphoma, B-Cell, Marginal ZoneAnti-Ulcer AgentsAmoxicillinCampylobacter InfectionsAntibodies, BacterialOmeprazoleClarithromycinLewis Blood-Group SystemCytotoxinsPolymerase Chain ReactionGenotypeDuodenumImmunohistochemistryPrevalenceAdenocarcinomaIntestinesAnemia, PerniciousParietal Cells, GastricSeverity of Illness IndexMexicoRisk FactorsGene Rearrangement, B-Lymphocyte, Heavy ChainImmunoglobulin GDNA, BacterialCase-Control StudiesProspective StudiesFollow-Up StudiesAnti-Bacterial AgentsPostgastrectomy SyndromesImmunoglobulin APepsinogensHyperplasiaRetrospective StudiesDrug Therapy, CombinationInterleukin-1betaPolymorphism, GeneticEndoscopyEnzyme-Linked Immunosorbent AssaySymptom AssessmentDepressionSensitivity and SpecificityAcinonyx