title: Helicobacter pylori in gastric cancer established by CagA immunoblot as a marker of past infection.
abstract: OBJECTIVE
  Helicobacter pylori may disappear spontaneously with progressing precancerous changes and invalidate serologic studies of its association with gastric cancer. We reestimated the strength of the H. pylori-gastric cancer relationship, using both conventional immunoglobulin (Ig) G enzyme-linked immunosorbent assay (ELISA) and immunoblot (against cytotoxin-associated antigen A [CagA] antibodies that prevail longer after eradication) to detect past H. pylori exposure more relevant for time at cancer initiation.
  
  
  METHODS
  In our population-based case-control study, the seroprevalence among 298 gastric adenocarcinoma cases was 72% (IgG ELISA) and 91% (immunoblot) vs. 55% and 56% among 244 controls frequency-matched for age and gender.
  
  
  RESULTS
  Using IgG ELISA only, the adjusted OR for noncardia gastric cancer among H. pylori-positive subjects was 2.2 (95% confidence interval [CI], 1.4-3.6). When ELISA-/CagA+ subjects (odds ratio [OR], 68.0) were removed from the reference, the OR rose to 21.0 (95% CI, 8.3-53.4) and the previous effect modification by age disappeared. ELISA+/CagA- subjects had an OR of 5.0 (95% CI, 1.1-23.6). There were no associations with cardia cancer.
  
  
  CONCLUSIONS
  The weaker H. pylori-cancer relationships in studies based on IgG ELISA rather than CagA may be caused by misclassification of relevant exposure. A much stronger relationship emerges with more accurate exposure classification. In the general Swedish population, 71% of noncardia adenocarcinomas were attributable to H. pylori.
authors.affiliation: Department of Medical Epidemiology, Karolinska Institutet, Stockholm, Sweden. Anna.Mia.Ekstrom@phs.ki.se
authors.forename: A M
authors.initials: AM
authors.lastname: Ekström
authors.forename: M
authors.initials: M
authors.lastname: Held
authors.forename: L E
authors.initials: LE
authors.lastname: Hansson
authors.forename: L
authors.initials: L
authors.lastname: Engstrand
authors.forename: O
authors.initials: O
authors.lastname: Nyrén
mesh_terms: D000230:Adenocarcinoma / Q000382:microbiology* / Q000473:pathology; D000293:Adolescent; D000328:Adult; D000942:Antigens, Bacterial / Q000032:analysis*; D001426:Bacterial Proteins / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D016481:Helicobacter Infections / Q000453:epidemiology*; D016480:Helicobacter pylori; D006801:Humans; D015151:Immunoblotting; D007074:Immunoglobulin G / Q000032:analysis; D007223:Infant; D008297:Male; D015999:Multivariate Analysis; D015995:Prevalence; D012016:Reference Values; D013274:Stomach Neoplasms / Q000145:classification / Q000382:microbiology* / Q000473:pathology; D013548:Sweden / Q000453:epidemiology
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D007074:Immunoglobulin G; C080866:cagA protein, Helicobacter pylori