• Sheila F O'Brien, Qi-Long Yi, Wenli Fan, Vito Scalia, Steven H Kleinman, and Eleftherios C Vamvakas.
• Canadian Blood Services, and the Department of Epidemiology & Community Medicine, University of Ottawa, Ottawa, Ontario, Canada. sheila.o'brien@bloodservices.ca
• Transfusion. 2007 Feb 1; 47 (2): 316-25.

BackgroundNew testing methods such as nucleic acid amplification testing (NAT) and chemiluminescent serologic assays have been introduced, more precise estimates for infectious window periods are available, and a new method for estimating the residual risk (RR) of transfusion-transmitted infections (TTIs) has been developed. Thus, available RR estimates for Canada need to be updated.Study Design And MethodsIncidence rates for known TTI markers were determined for all allogeneic whole-blood donations made to Canadian Blood Services between 2001 and 2005; they were derived from NAT conversions or seroconversions of repeat donors with at least two donations in a 3-year period. RR estimates for human immunodeficiency virus (HIV)-1 and hepatitis C virus (HCV) derived from the classical incidence/window-period model were compared to those obtained by the new method that estimates incidence from NAT-positive, antibody-negative donations (NAT-yield cases) from all donors divided by person-years.ResultsWith the classical method, the RR of HIV (1 per 7.8 million donations) and HCV (1 per 2.3 million) were low; HBV RR was higher (1 per 153,000). HCV RR was significantly lower when estimated with the new method (1 per 13 million). Eleven HCV NAT-yield cases were predicted by applying the classical method to our seroconversion data but only 2 were observed (p = 0.011). Observed HIV-1 NAT-yield cases (n = 1) matched those predicted (n = 0.7).ConclusionNew tests have reduced an already low risk of TTI in Canada. HCV RR estimates by two different methods differed but both were low.

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