title: An international collaborative study to establish a World Health Organization international standard for hepatitis B virus DNA nucleic acid amplification techniques.
abstract: OBJECTIVE
  Twenty-two laboratories from nine countries participated in an international collaborative study to establish a World Health Organization (WHO) international standard for hepatitis B virus (HBV) DNA nucleic acid amplification techniques (NAT).
  
  
  METHODS
  Three samples, AA, BB (both of which were lyophilized) and CC (which was a liquid preparation), were analysed using several different NAT assays. The mean HBV DNA content of each sample was determined from the study.
  
  
  RESULTS
  Despite the range of assays (commercial and in-house) used by participants, there was good agreement among the overall mean 'equivalents'/ml obtained by the different assays, except for one laboratory (laboratory 4). The variation in estimates of log10 'equivalents'/ml was 1.75-1.25 for the three samples if results from laboratory 4 were excluded. The mean log10 'equivalents'/ml for all laboratories were 6.42 for sample AA, 6.30 for sample BB and 5.03 for sample CC (exclusion of results from laboratory 4 made little difference). The difference in titres between the two lyophilized samples (AA and BB) was not statistically significant but the titre of the frozen sample (CC) was significantly lower. Material AA (code 97/746) was accepted as the first WHO international standard for HBV DNA NAT assays and assigned a potency of 10(6) international units (IU)/ml.
  
  
  CONCLUSIONS
  The titres (genome equivalents/ml) of three HBV preparations were determined by several laboratories using different NAT assays. This study enabled the establishment of an international standard, 97/746, for HBV DNA NAT assays.
authors.affiliation: Division of Virology, National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Herts EN6 3QG, UK. jsaldanha@nibsc.ac.uk
authors.forename: J
authors.initials: J
authors.lastname: Saldanha
authors.forename: W
authors.initials: W
authors.lastname: Gerlich
authors.forename: N
authors.initials: N
authors.lastname: Lelie
authors.forename: P
authors.initials: P
authors.lastname: Dawson
authors.forename: K
authors.initials: K
authors.lastname: Heermann
authors.forename: A
authors.initials: A
authors.lastname: Heath
mesh_terms: D004279:DNA, Viral / Q000097:blood / Q000302:isolation & purification / Q000592:standards*; D006509:Hepatitis B / Q000097:blood / Q000175:diagnosis*; D006515:Hepatitis B virus / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D015588:Observer Variation; D016133:Polymerase Chain Reaction / Q000379:methods / Q000592:standards*; D012015:Reference Standards; D012107:Research Design; D014766:Viremia / Q000097:blood / Q000175:diagnosis*; D014773:Virology / Q000592:standards*; D014944:World Health Organization
chemical_list: D004279:DNA, Viral