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PROFICIENCY TESTING OF IN-HOUSE NAT ASSAYS USED FOR BLOOD SCREENING

PROFICIENCY TESTING OF IN-HOUSE NAT ASSAYS USED FOR BLOOD SCREENING. XXI SoGAT International Working Group Meeting on the Standardization of NAT for the Safety Testing of Blood, Tissues and Organs for Blood-Borne Pathogens 28 - 29 May 2009 Brussels, Belgium. Julia Kreß Michael Chudy

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PROFICIENCY TESTING OF IN-HOUSE NAT ASSAYS USED FOR BLOOD SCREENING

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  1. PROFICIENCY TESTING OF IN-HOUSE NAT ASSAYS USED FOR BLOOD SCREENING XXI SoGAT International Working Group Meeting on the Standardization of NAT for the Safety Testing of Blood, Tissues and Organs for Blood-Borne Pathogens 28 - 29 May 2009 Brussels, Belgium Julia Kreß Michael Chudy Micha Nübling Paul-Ehrlich-Institut, Langen, Germany WHO Collaborating Centre for Quality Assurance of Blood Products and in vitro Diagnostic Devices

  2. German Regulations for NAT Blood Donor Screening • 1999: first mandatory NAT was introduced for HCV (< 5.000 IU/mL ID) • 2004: NAT was implemented for HIV-1 (< 10.000 IU/mL ID) • HBV NAT is voluntarily performed by many blood donation services • in-house developed NAT assays, CE-marked diagnostic assays (off-label-use) and CE-marked NAT screening assays may be used • assays are validated for the individual pool size (10 to 96 donations) • validation studies are assessed by PEI • NAT systems undergo regular external quality assessment programs organised by PEI • 2008: proficiency study for in-house NAT assays: HCV, HIV-1 and HBV 1

  3. In-house NAT Proficiency Study 2008: Objective • verification of the efficiency of in-house NAT assays for the detection of HCV, HIV-1 and HBV in blood donations regarding • analytical sensitivity • genotype / subtype sensitivity • specificity • reproducibility • the participation in the proficiency study is mandatory for HCV and HIV-1 NATs, voluntary for HBV NAT 2

  4. In-house NAT Proficiency Study 2008: Study Design • detection limit of the HCV, HIV-1 and HBV NATs with respect to the pool size • testing panels: calibrated PEI reference preparation, two positive materials and negative plasma • HIV-1-samples: one missed by CTM v1, one with discrepant results • 0.5 log dilution series starting with the required minimum sensitivity • characterization of panels by CE-certified NAT screening systems: cobas TaqScreen MPX Test, Procleix Ultrio Assay • dilution of samples individually for each lab simulating the pool size • encoding of labs and samples • sample shipment on dry ice • submission of qualitative results (reactive / non-reactive) 3

  5. In-house NAT Proficiency Study 2008: Participants • Invited laboratories: • in-house NAT screening assays (non-CE-marked / CE-marked) • CE-marked diagnostic assays used for screening (off-label-use) • CE-marked screening system with large pool sizes (48, 96) • HCV: 30 labs 16 in-house NATs, 16 diagnostic assays, 3 cobas TaqScreen MPX (5 labs: 2 different methods) • HIV-1: 30 labs 15 in-house NATs, 15 diagnostic assays, 3 cobas TaqScreen MPX (3 labs: 2 different methods) • HBV: 21 labs 14 in-house NATs, 6 diagnostic assays, 3 cobas TaqScreen MPX (2 labs: 2 different methods) 4

  6. In-house NAT Proficiency Study 2008: HCV Results 5

  7. In-house NAT Proficiency Study 2008: HIV-1 Results 6

  8. In-house NAT Proficiency Study 2008: HBV Results 7

  9. In-house NAT Proficiency Study 2008: Conclusion • all participants meet the PEI sensitivity requirements • in most labs NAT assays show higher sensitivity than required • high specificity: only 1 false-positive result by 1 lab • HIV-1: CTM v1-missed sample was detected by other systems • due to high mutation rates there is a certain amount of risk that infectious donations are missed by HIV-1 NATs • voluntary HBV NAT assays: high sensitivity and specificity • in-house NAT systems and off-label-use systems under proper conditions are still suitable for blood donor screening 8

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