| Since we prepared our first Eurohep reference panel in 1992 several HCV standards of different genotypes have been tested in VQC proficiency programs and in validation studies. Over the years the HCV-RNA concentration in the VQC-Sanquin HCV genotype 1 standard has been quantified in copies/mL by several methods, but the results of the bDNA 3.0 assay have been used as the reference method for calibration. Thereafter the VQC-Sanquin standard has been compared with the 1st and 2nd International Standards in two WHO collaborative studies. When taking the calibration data of these and other multi-center studies together the number of HCV-RNA copies per IU (95% CI) was estimated at 2.73 (1.4-4.8). We also calibrated a chimpanzee plasma of known infectivity against the VQC-Sanquin standard and the 50% minimum infectious dose (range) was estimated at 8.1 (2.6-25.6) HCV-RNA copies or virions.
Our company has prepared several batches of dilution panels from the 1st, 2nd and 3rd WHO standards which over time have been tested in hundreds of replicates in validation studies of the Procleix Ultrio versions. Consistent 95% and 50% LODs were found on all standards, but for the 3rd WHO HCV 06/100 standard significantly higher LODs were found over time (indicating reduced stability of the lyophilised virus). Our degradation studies at different temperatures show significantly higher stability of the VQC-Sanquin genotype 1 standard at -30˚C and 4˚C than of the WHO 06/100 standard. Since the VQC-Sanquin standard is directly traceable to the 1st WHO 96/790 and 2nd WHO 96/798 standards one can use our more stable standard dilution panels for estimating 95% and 50% LODs in IU/mL.
All other HCV genotype standards have been calibrated against the VQC-Sanquin standard in multiple replicate bDNA 3.0 assays, including an inactivated genotype 3a standard used for preparation of the ViraQ Controls.
The ten member HCV genotype standard dilution panels starting at around 3000 copies/mL will be replaced by 8 member panels composed of 300, 100, 30, 10, 3, 1, 0.3 and 0.1 copies/mL. The package insert gives an overview of all HCV genotype standard dilution panels and the proportion of reactive results in different NAT methods. Product Insert.pdf Material Safety Data Sheet.pdf
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