title: Absence of occult hepatitis B among blood donors in southern Brazil.
abstract: BACKGROUND
  Occult hepatitis B virus (HBV) infection is characterized by the detection of HBV DNA in serum and/or in liver in the absence of detectable hepatitis B surface antigen (HBsAg). The reported prevalence of occult hepatitis B varies markedly among populations and according to the sensitivity of the HBV DNA assay. The aim of the present study was to describe the prevalence of occult hepatitis B among HCV-infected and non-infected blood donors in Porto Alegre, Southern Brazil, using a highly sensitive real time polymerase chain reaction (PCR) method.
  
  
  METHODS
  Between 1995 and 1997 a sample of 178 blood donors with two positive anti-HCV ELISA tests were consecutively selected as cases, and 356 anti-HCV negative donors were selected as controls. Blood donors were randomly selected from eight blood centers in Porto Alegre, Southern Brazil, representative of the whole blood donor population. Blood samples were kept at 70ºC and defrosted for the first time for the analysis of this report. Tests previously performed in the laboratory using the same real time PCR for HBV DNA had sensitivity for detecting as low as 9 copies/mL. Among 158 blood samples from HBsAg-negative blood donors, five were anti-HBc positive, 53 tested positive for anti-HCV and 105 had anti-HCV negative. The samples analysis was performed in duplicate and all blood samples tested negative for HBV DNA.
  
  
  CONCLUSIONS
  The result reflects a very low prevalence of occult hepatitis B in our setting.
authors.affiliation: National Institute of Science and Technology for Health Technology Assessment, Rua Dr. Freire Alemao 351 /703, Porto Alegre, RS, Brazil. fhwolff@gmail.com
authors.forename: Fernando Herz
authors.initials: FH
authors.lastname: Wolff
authors.forename: Sandra Costa
authors.initials: SC
authors.lastname: Fuchs
authors.forename: Ajacio B M
authors.initials: AB
authors.lastname: Brandão
mesh_terms: D001782:Blood Donors / Q000706:statistics & numerical data*; D001938:Brazil / Q000453:epidemiology; D016022:Case-Control Studies; D004279:DNA, Viral / Q000097:blood*; D006509:Hepatitis B / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D006510:Hepatitis B Antibodies / Q000097:blood*; D006515:Hepatitis B virus / Q000235:genetics*; D006526:Hepatitis C / Q000150:complications*; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods; D015995:Prevalence; D012680:Sensitivity and Specificity
chemical_list: D004279:DNA, Viral; D006510:Hepatitis B Antibodies