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

Presentation Transcript

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

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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verification of the efficiency of in-house NAT assays for the detection of HCV, HIV-1 and HBV in blood donations regarding

the participation in the proficiency study is mandatory for HCV and HIV-1 NATs, voluntary for HBV NAT

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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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16 in-house NATs, 16 diagnostic assays, 3 cobas TaqScreen MPX (5 labs: 2 different methods)

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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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