World Health Organization collaborative study to establish a replacement WHO international standard for hepatitis C virus RNA nucleic acid amplification technology assays

Background and Objectives A collaborative study was undertaken to establish a replacement for the current (1st) World Health Organization (WHO) hepatitis C virus (HCV) International Standard, 96/790. Materials and Methods Both the 1(st) International Standard and the replacement standard were prepared from the same starting material by diluting a high titre genotype 1a HCV isolate in pooled, human plasma. The only difference was that each standard was lyophilized in two, separate lyophilisation runs but under the same conditions. Results In the study to establish the 1st International Standard, no significant difference in potency was found between the material eventually designated as the 1st International Standard and that now selected as the 2nd International Standard. The present study also showed no significant differences between the materials stored at -20 degrees C and no evidence of degradation over 5 years. Conclusions Material 96/798 was established as the 2nd HCV International Standard and assigned the same unitage as the 1st International Standard, i.e. 10(5) IU/ml (50 000 IU/vial).