World Health Organization collaborative study to calibrate the 3rd International Standard for Hepatitis C virus RNA nucleic acid amplification technology (NAT)-based assays

Vox Sang. 2011 May;100(4):409-17. doi: 10.1111/j.1423-0410.2010.01434.x. Epub 2010 Dec 13.


Background and objectives: A collaborative study was undertaken to evaluate a replacement World Health Organization International Standard for hepatitis C virus (HCV) RNA for nucleic acid amplification technology (NAT)-based assays. The candidate preparations were calibrated in International Units (IUs).

Materials and methods: Three new candidate preparations were produced from a single bulk containing anti-HCV-negative, genotype 1a HCV RNA-positive plasma. Two samples were lyophilized (coded Sample 2 and Sample 3), whilst a third (Sample 4) contained liquid/frozen material. The samples were distributed together with the 2(nd) International Standard (Sample 1, NIBSC code 96/798) for evaluation by thirty-three laboratories, from fourteen countries. The panel of samples were assayed on four separate occasions. Stability studies were performed for the lyophilized samples by accelerated thermal degradation.

Results: Participants returned data from a wide range of commercial and in-house quantitative and qualitative assays. Twenty-five data sets were returned for quantitative assays and fourteen for qualitative assays. Excellent agreement was observed between laboratories and assay methods. The mean relative potencies of Samples 2-4 were 5·19, 5·41 and 5·70 log(10) IU/ml, respectively, when compared against the 2(nd) International Standard. Samples 2 and 3 demonstrated stability of a similar order to the previous standards.

Conclusions: Based upon the results of the collaborative study, Sample 2 (code number 06/100) was established as the 3rd International Standard for HCV RNA with an assigned unitage of 5·19 log(10) IU/ml. Each vial contains the equivalent of 0·5 ml of material; each vial contains 4·89 log(10) IU of HCV RNA.

Publication types

  • Comparative Study
  • Multicenter Study

MeSH terms

  • Calibration
  • Female
  • Hepacivirus*
  • Hepatitis C / blood*
  • Hepatitis C / genetics
  • Humans
  • Male
  • Nucleic Acid Amplification Techniques / methods
  • Nucleic Acid Amplification Techniques / standards*
  • RNA, Viral / blood*
  • RNA, Viral / genetics
  • Reference Standards
  • Sensitivity and Specificity
  • World Health Organization


  • RNA, Viral