title: Helicobacter pylori Infection in Thailand: A Nationwide Study of the CagA Phenotype.
abstract: BACKGROUND
  The risk to develop gastric cancer in Thailand is relatively low among Asian countries. In addition, the age-standardized incidence rate (ASR) of gastric cancer in Thailand varies with geographical distribution; the ASR in the North region is 3.5 times higher than that in the South region. We hypothesized that the prevalence of H. pylori infection and diversity of CagA phenotype contributes to the variety of gastric cancer risk in various regions of Thailand.
  
  
  METHODS
  We conducted a nationwide survey within Thailand. We determined H. pylori infection prevalence by detecting H. pylori, using histochemical and immunohistochemical methods. The anti-CagA antibody and anti-East-Asian type CagA antibody (α-EAS Ab), which showed high accuracy in several East Asian countries, were used to determine CagA phenotype.
  
  
  RESULTS
  Among 1,546 patients from four regions, including 17 provinces, the overall prevalence of H. pylori infection was 45.9% (710/1,546). Mirroring the prevalence of H. pylori infection, histological scores were the lowest in the South region. Of the 710 H. pylori-positive patients, 93.2% (662) were immunoreactive with the anti-CagA antibody. CagA-negative strain prevalence in the South region was significantly higher than that in other regions (17.9%; 5/28; p < 0.05). Overall, only 77 patients (11.6%) were immunoreactive with the α-EAS Ab. There were no differences in the α-EAS Ab immunoreactive rate across geographical regions.
  
  
  CONCLUSIONS
  This is the first study using immunohistochemistry to confirm H. pylori infections across different regions in Thailand. The prevalence of East-Asian type CagA H. pylori in Thailand was low. The low incidence of gastric cancer in Thailand may be attributed to the low prevalence of precancerous lesions. The low incidence of gastric cancer in the South region might be associated with the lower prevalence of H. pylori infection, precancerous lesions, and CagA-positive H. pylori strains, compared with that in the other regions.
authors.affiliation: Department of Molecular Pathology, Oita University Faculty of Medicine, Hasama-machi, Yufu-City, Oita, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Uchida
authors.affiliation: Department of Environmental and Preventive Medicine, Oita University Faculty of Medicine, Hasama-machi, Yufu-City, Oita, Japan; Institute of Tropical Disease, Airlangga University, Surabaya, Indonesia.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Miftahussurur
authors.affiliation: Division of Gastroenterology, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Rapat
authors.initials: R
authors.lastname: Pittayanon
authors.affiliation: Gastroenterology Unit, Thammasat University Hospital, Pathumthani, Thailand.
authors.forename: Ratha-Korn
authors.initials: RK
authors.lastname: Vilaichone
authors.affiliation: Department of Pathology, Chulalongkorn University Hospital, Bangkok, Thailand.
authors.forename: Naruemon
authors.initials: N
authors.lastname: Wisedopas
authors.affiliation: Department of Surgery, Rajavithi Hospital, Bangkok, Thailand.
authors.forename: Thawee
authors.initials: T
authors.lastname: Ratanachu-Ek
authors.affiliation: Department of Forensic Medicine, Oita University Faculty of Medicine, Hasama-machi, Yufu-City, Oita, Japan.
authors.forename: Tetsuko
authors.initials: T
authors.lastname: Kishida
authors.affiliation: Department of Molecular Pathology, Oita University Faculty of Medicine, Hasama-machi, Yufu-City, Oita, Japan.
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Moriyama
authors.affiliation: Department of Environmental and Preventive Medicine, Oita University Faculty of Medicine, Hasama-machi, Yufu-City, Oita, Japan; Department of Medicine-Gastroenterology, Baylor College of Medicine and Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, United States of America.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Yamaoka
authors.affiliation: Gastrointestinal and Liver Center, Bangkok Medical Center, Bangkok, Thailand.
authors.forename: Varocha
authors.initials: V
authors.lastname: Mahachai
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000942:Antigens, Bacterial / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D004724:Endoscopy; D005260:Female; D005753:Gastric Mucosa / Q000473:pathology; D005756:Gastritis / Q000382:microbiology; D005843:Geography; D016481:Helicobacter Infections / Q000453:epidemiology* / Q000382:microbiology*; D016480:Helicobacter pylori / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D015995:Prevalence; D011795:Surveys and Questionnaires; D013785:Thailand / Q000453:epidemiology; D016896:Treatment Outcome
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C080866:cagA protein, Helicobacter pylori