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

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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

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

german regulations for nat blood donor screening
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

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in house nat proficiency study 2008 objective
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

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in house nat proficiency study 2008 study design
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)

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in house nat proficiency study 2008 participants
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)

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in house nat proficiency study 2008 conclusion
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

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