Background and Objectives In Canada, transfusion transmission risk of Human T-cell lymphotropic virus -I/II (HTLV) is addressed by universal leucoreduction and universal antibody testing. We aimed to estimate the risk with the current policy, if testing only first-time donors and if testing were stopped.
Materials and MethodsMonte Carlo simulation was employed to estimate the proportion of red cell concentrate, random donor platelet and apheresis platelet units that would be released into inventory in each scenario (10 billion donors each). The model estimated the number of HTLV-positive donations not intercepted by testing, randomly assigned the number of HTLV particles/100 leucocytes using proportions from published data and randomly selected a postleucoreduction leucocyte count from quality control data. Units were considered infectious if ≥9 9 10 4 copies of HTLV provirus.Results With universal leucoreduction in place, the residual risk of releasing an HTLV potentially infectious unit with universal testing was 1 in 1Á2 billion units (0, 1 in 55Á9 million), with testing only first-time donors 1 in 7Á1 million (0, 1 in 1Á05 million) and with no testing 1 in 1Á0 million (0, 1 in 178 600). The efficacy of leucoreduction was >99Á5% (lower bound 95Á7%) for all scenarios.Conclusion With universal leucoreduction in place, switching from universal testing to testing first-time donors would incur very low risk.