title: Residual risk of HIV, HCV and HBV in Canada.
abstract: BACKGROUND
  Residual risk is estimated as the product of the incidence and the infectious window period, the time during which a blood donation could be infectious but the assay may not detect it. In 2011 nucleic acid multiplex testing (MPX) was implemented in 6 unit minipools (previously 24 unit minipools). MPX also included hepatitis B (HBV) NAT for the first time (complementing HBsAg screening) in addition to HIV-1 and hepatitis C (HCV) as before. We aimed to estimate window period risk-day equivalents for MPX, and the residual risk of viral infections in blood donations updated to reflect current incidence and testing.
  
  
  METHODS
  Transmissible disease conversions of repeat donations to Canadian Blood Services within the three-year period 2012-2014 divided by person-years estimated incidence for HIV, HCV and HBV (adjusted for transient viremia). Window period risk-day equivalents for MPX were estimated using a published method. Residual risk was the product of incidence and window period risk-day equivalents. 95% confidence intervals were estimated using Monte Carlo simulation of the window period risk-day equivalents and the incidence density 95% confidence intervals.
  
  
  RESULTS
  The incidence rate per 100,000 person years for HIV was 0.28, HCV 1.0 and HBV 0.26. The residual risk of HIV was 1 per 21.4 million donations, HCV 1 per 12.6 million donations and HBV 1 per 7.5 million donations.
  
  
  CONCLUSIONS
  The residual risk of infection is very low, similar to 2006-2009. The safety benefit of further shortening of the infectious window period is below the threshold to quantify.
authors.affiliation: Canadian Blood Services, Canada; Dept. of Epidemiology & Community Medicine, University of Ottawa, Canada. Electronic address: sheila.obrien@blood.ca.
authors.forename: Sheila F
authors.initials: SF
authors.lastname: O'Brien
authors.affiliation: Canadian Blood Services, Canada; Dept. of Epidemiology & Community Medicine, University of Ottawa, Canada.
authors.forename: Qi-Long
authors.initials: QL
authors.lastname: Yi
authors.affiliation: Canadian Blood Services, Canada.
authors.forename: Wenli
authors.initials: W
authors.lastname: Fan
authors.affiliation: Canadian Blood Services, Canada.
authors.forename: Vito
authors.initials: V
authors.lastname: Scalia
authors.affiliation: Canadian Blood Services, Canada; Dept. of Pathology & Laboratory Medicine, University of Ottawa, Canada.
authors.forename: Mindy
authors.initials: M
authors.lastname: Goldman
authors.affiliation: Canadian Blood Services, Canada; Dept. of Medical Microbiology, University of Toronto, Canada.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Fearon
mesh_terms: D002170:Canada / Q000453:epidemiology; D015658:HIV Infections / Q000453:epidemiology*; D006509:Hepatitis B / Q000453:epidemiology*; D006526:Hepatitis C / Q000453:epidemiology*; D006801:Humans; D012307:Risk Factors
keywords: Incidence; Multiplex NAT; Residual risk