WHO/BS/2019.2358 WHO 6th IS for HCV RNA for NAT

Overview

This report describes the preparation and evaluation of two candidates for the proposed 6 th WHO International Standard (IS) for hepatitis C virus (HCV) RNA for nucleic acid amplification techniques (NAT). Both candidates were prepared from the same HCV RNA positive plasma donation diluted in pooled human plasma and lyophilized in separate runs. Nineteen laboratories from 12 countries evaluated the suitability of each candidate using their routine HCV NAT-based assay. Candidates 18/184 (sample 1) and 18/198 (sample 2) were evaluated alongside the 5 th HCV IS, NIBSC code 14/150 (sample 3), two inactivated cell cultured HCV (HCVcc) samples (4 and 5) and three HCV-positive plasma samples comprising different HCV genotypes (samples 6-8). A range of HCV NAT assays were used in the evaluation, the majority of which were commercial quantitative assays based on realtime PCR technology.

The variability of HCV RNA measurements between laboratories (SD of individual laboratory mean potency estimates) ranged from 0.11 to 0.28 log10 IU/mL across the eight study samples. HCV RNA measurements from qualitative assays were higher than those from quantitative assays. When potencies were expressed relative to study samples 1-5 there was little change in inter-laboratory variability. This would suggest that overall HCV NAT assays are well harmonized. Candidates 1 and 2 demonstrated slightly better harmonization than the existing HCV IS highlighting the suitability of both candidates to harmonize HCV NAT. HCVcc samples comprising different genotypes did not significantly worsen the agreement between HCV NAT assays and could be explored further as an alternative source material for replacement HCV ISs.

Data from accelerated thermal degradation studies suggests that there are differences in the stability of both candidates. The data suggests that candidate 18/184 is sufficiently stable upon prolonged storage at -20 °C. Meanwhile, the data for 18/198 suggests that this candidate might not be stable in the long-term, although this needs further investigation. Additional data on the short-term stability of both candidates is needed before an established replacement can be shipped at ambient temperature. Existing stability data suggests that both candidates would be stable during shipping at temperatures of 20 °C and below.

It is recommended that candidate 18/184 (sample 1) is established as the 6 th WHO IS for HCV RNA for NAT with a potency of 5.41 log10 (2.57×105 ) IU/vial. The proposed potency is based on the robust method mean of all assay results relative to the 5th HCV IS. The standard is intended for the calibration of secondary references comprising HCV plasma used in HCV NAT.