title: An international collaborative study to establish the 2nd World Health Organization International Standard for hepatitis B virus DNA nucleic acid amplification technology-based assays.
abstract: OBJECTIVE
  The aim of this study was to replace the 1st World Health Organization International Standard for hepatitis B virus DNA for nucleic acid amplification technique (NAT)-based assays (code 97/746) with a new International Standard. Two lyophilized preparations freeze dried from the same bulk were evaluated in the original collaborative study (coded 97/746 and 97/750, and termed AA and BB, respectively, in the original study). This present study re-evaluates these two preparations in terms of potency and real-time stability.
  
  
  METHODS
  The 1(st) International Standard (97/746) and the second lyophilized preparation (97/750) were coded Samples 1 and 2, respectively, in the present study. The samples were distributed to six laboratories and assayed on four separate occasions. Accelerated thermal degradation samples of the two preparations were examined after long-term storage at 4 degrees C and 20 degrees C for more than 51 months.
  
  
  RESULTS
  Data were returned from a total of nine different NAT-based assays, five in qualitative format and four in quantitative format. The results of this study confirm the results of the original collaborative study, with no significant differences being found in estimated international units (IU)/ml or polymerase chain reaction-detectable units/ml for the 1(st) International Standard (Sample 1 in this study) and the proposed replacement preparation, Sample 2 (97/750). Real-time and accelerated degradation studies indicate that both samples are very stable. Storage of both preparations at 20 degrees C for more than 51 months resulted in no detectable degradation.
  
  
  CONCLUSIONS
  On the basis of the data presented in this collaborative study, Sample 2 (code 97/750) was established as the 2nd International Standard for hepatitis B virus DNA for NAT-based assays with a potency of 10(6) IU/ml (500,000 IU/vial).
authors.affiliation: National Institute for Biological Standards and Control, Potters Bar, Hertfordshire, UK. baysa@pei.de
authors.forename: S A
authors.initials: SA
authors.lastname: Baylis
authors.forename: A B
authors.initials: AB
authors.lastname: Heath
authors.forename: M
authors.initials: M
authors.lastname: Chudy
authors.forename: G
authors.initials: G
authors.lastname: Pisani
authors.forename: A
authors.initials: A
authors.lastname: Klotz
authors.forename: S
authors.initials: S
authors.lastname: Kerby
authors.forename: W
authors.initials: W
authors.lastname: Gerlich
mesh_terms: D004279:DNA, Viral / Q000032:analysis*; D006509:Hepatitis B / Q000175:diagnosis*; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D021141:Nucleic Acid Amplification Techniques / Q000379:methods / Q000592:standards*; D012015:Reference Standards; D014944:World Health Organization
chemical_list: D004279:DNA, Viral