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International Units vs. NAT-Detectable Units

XX. SoGAT Meeting Warsaw 12./13. June 2007 IU vs. NAT-Detectable Units Albrecht Gröner CSL Behring Virology Marburg, Germany. International Units vs. NAT-Detectable Units. International Units inter-laboratory comparison of results (e.g., virus load in samples)

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International Units vs. NAT-Detectable Units

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  1. XX. SoGAT MeetingWarsaw 12./13. June 2007IU vs. NAT-Detectable UnitsAlbrecht GrönerCSL BehringVirologyMarburg, Germany

  2. International Units vs. NAT-Detectable Units • International Units • inter-laboratory comparison of results (e.g., virus load in samples) • release of pools for fractionation (e.g., OMCLs) • NAT-detectable units (genome equivalent (GE)) • detection of virus genomes in samples • intra-laboratory comparison of results (if assay performance is very stable) 2 – Gröner 13. June 2007

  3. Conversion Factor IU  GE • Necessity to define conversion factor • quantification of virus particles in sample defined by NAT in order to assess risk for virus transmission • CPMP/BWP/5180/03 (Guideline on assessing the risk for virus transmission – new chapter 6 of the note for guidance on plasma-derived medicinal products (CPMP/BWP/269/95)) requests a quantitative estimation of the probability of a virus contaminant being present in a defined dose of final product taking into account - as a conservative approach - viral genomes as an indicator of potentially infectious virus particles in the starting material 3 – Gröner 13. June 2007

  4. Fig 1a: 97/656 International Standard 14 13 12 NIBSC - 2002 11 10 HIV 9 8 7 27 UCM 6 60 64 N M 5 17 22 04 N TMA M 4 67 17 63 M* IH M 3 30 09 61 CAS CM M 2 59 14 58 56 48 N IH B3 B3 M 1 12 19 54 45 65 05 57 CM IH CAS IH AL AS CM 0 neg 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Ecstimated RNA Copies or PCR Detectable Units (log10/ml) Detection of Virus Genome in Sample 4 – Gröner 13. June 2007

  5. Fig 1h: RU570 Subtype H (S02) 14 13 12 11 NIBSC - 2002 10 HIV 9 8 7 6 5 61 M 4 30 27 56 CAS UCM M 3 64 58 60 09 63 N B3 M CM M* 2 48 17 14 22 05 17 N TMA B3 M CM M 1 04 12 67 54 65 45 59 19 57 N IH IH IH AS AL IH CAS CM 0 neg 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Estimated RNA Copies or PCR Detectable Units (log10/ml) Monitor assays Nuclisens bDNA 3 Abbott LCx In-House Ampliscreen TMA Detection of Virus Genome in Sample 5 – Gröner 13. June 2007

  6. Detection of Virus Genome in Sample HIV NIBSC - 2002 6 – Gröner 13. June 2007

  7. Detection of Virus Genome in Sample HAV International Standard Saldanha et al. Vox Sang 2005;89:52-58 7 – Gröner 13. June 2007

  8. Detection of Virus Genome in Sample HCV International Standard Saldanha et al. Vox Sang 1999;76:149-158 8 – Gröner 13. June 2007

  9. Conversion Factor IU  GE • Is a general conversion factor necessary (and justifiable)? • Conversion factor can only be determined for each laboratory employing a validated assay • A generic conversion factor for IUs to GE is not appropriate due to differences in analytical sensitivity of assays in different laboratories • Quantitative infectivity of viruses (inf. units) vs. NAT detectable units unknown Relevance of Conversion Factor? 9 – Gröner 13. June 2007

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