title: Independent and additive effect modification of hepatitis C and B viruses infection on the development of chronic hepatitis.
abstract: OBJECTIVE
  This study aimed to assess the effects and interaction between hepatitis B virus and hepatitis C virus infection on the development of chronic hepatitis.
  
  
  METHODS
  Anti-HCV and HBsAg were detected in 125 histology-proven chronic hepatitis and 250 sex-matched and age-matched healthy controls.
  
  
  RESULTS
  The prevalences of anti-HCV (24.8%) and HBsAg (68.0%) in patients were higher than in controls (2.4% and 18.0%, respectively; each p < 0.0001). Univariate analysis showed that anti-HCV and HBsAg were strongly associated with the development of chronic hepatitis. Calculation of synergy index and Mantel extension test for trend indicated that there was additive effect modification between HCV and HBV. Multivariate analysis indicated that anti-HCV (odds ratio, 46.1; 95% confidence interval, 9.1-233.2) and HBsAg (odds ratio, 25.8; 95% confidence interval (9.3-67.2) were independent risk factors of chronic hepatitis. The population-attributable risk was estimated as 15.6% for anti-HCV alone, 52.4% for HBsAg alone and 6.8% for both anti-HCV and HBsAg. The frequency of chronic active hepatitis in patients with anti-HCV alone (100%) was higher than in patients with HBsAg alone (75%, p < 0.001).
  
  
  CONCLUSIONS
  HCV and HBV infections are risk factors of chronic hepatitis. They act independently and probably with additive effect modification.
authors.affiliation: Department of Internal Medicine, Kaohsiung Medical College, Taiwan, Republic of China.
authors.forename: J F
authors.initials: JF
authors.lastname: Tsai
authors.forename: J E
authors.initials: JE
authors.lastname: Jeng
authors.forename: M S
authors.initials: MS
authors.lastname: Ho
authors.forename: W Y
authors.initials: WY
authors.lastname: Chang
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Lin
authors.forename: J H
authors.initials: JH
authors.lastname: Tsai
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D016174:Hepacivirus / Q000276:immunology*; D006509:Hepatitis B / Q000150:complications* / Q000276:immunology; D006514:Hepatitis B Surface Antigens / Q000276:immunology*; D006515:Hepatitis B virus / Q000276:immunology*; D006526:Hepatitis C / Q000150:complications* / Q000276:immunology; D018937:Hepatitis C Antibodies / Q000276:immunology*; D006521:Hepatitis, Chronic / Q000453:epidemiology / Q000209:etiology* / Q000276:immunology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: D006514:Hepatitis B Surface Antigens; D018937:Hepatitis C Antibodies