title: Current incidence and estimated residual risk of transfusion-transmitted infections in donations made to Canadian Blood Services.
abstract: BACKGROUND
  New 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.
  
  
  METHODS
  Incidence 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.
  
  
  RESULTS
  With 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).
  
  
  CONCLUSIONS
  New tests have reduced an already low risk of TTI in Canada. HCV RR estimates by two different methods differed but both were low.
authors.affiliation: Canadian Blood Services, and the Department of Epidemiology & Community Medicine, University of Ottawa, Ottawa, Ontario, Canada. sheila.o'brien@bloodservices.ca
authors.forename: Sheila F
authors.initials: SF
authors.lastname: O'Brien
authors.forename: Qi-Long
authors.initials: QL
authors.lastname: Yi
authors.forename: Wenli
authors.initials: W
authors.lastname: Fan
authors.forename: Vito
authors.initials: V
authors.lastname: Scalia
authors.forename: Steven H
authors.initials: SH
authors.lastname: Kleinman
authors.forename: Eleftherios C
authors.initials: EC
authors.lastname: Vamvakas
mesh_terms: D001771:Blood Banks / Q000706:statistics & numerical data*; D001782:Blood Donors; D001803:Blood Transfusion / Q000706:statistics & numerical data*; D002170:Canada / Q000453:epidemiology; D016208:Databases, Factual; D015658:HIV Infections / Q000097:blood / Q000453:epidemiology / Q000635:transmission; D006679:HIV Seropositivity; D015497:HIV-1; D015498:HIV-2; D015490:HTLV-I Infections / Q000097:blood / Q000453:epidemiology / Q000635:transmission; D006509:Hepatitis B / Q000097:blood / Q000453:epidemiology / Q000635:transmission; D006526:Hepatitis C / Q000097:blood / Q000453:epidemiology / Q000635:transmission; D006801:Humans; D015994:Incidence; D012307:Risk Factors; D065227:Transfusion Reaction; D014777:Virus Diseases / Q000097:blood / Q000453:epidemiology* / Q000635:transmission*