Recent Canadian experience with targeted hepatitis C virus lookback

Targeted hepatitis C virus (HCV) lookback studies have been performed in Canada since 1995. The yield of HCV lookback has not been reassessed since the introduction of improved HCV screening tests.

Data were combined from the two Canadian blood suppliers to determine the yield of targeted HCV lookback performed on donors found to be HCV-positive by antibody screening and/or nucleic acid testing (NAT) from the introduction of NAT in 1999 until January 1, 2005.

Lookback was performed on 498 donations from 176 HCV-seropositive and two NAT-only-positive donors; 494 components had been transfused, and 160 components were traced to living recipients who underwent HCV testing. Seventy-two percent of recipients of components derived from donations given before the introduction of second-generation enzyme immunoassay (EIA) testing were HCV-seropositive. Four recipients of components derived from donations tested by second- or third-generation EIA, with or without NAT, were HCV-seropositive. Two of these recipients tested HCV-seropositive before transfusion, and a third was probably infected by transfusions before the introduction of HCV testing. The fourth recipient likely received a noninfectious transfusion, since five other recipients of components from subsequent donations made by this donor were seronegative.

When previous donations had been tested by second- or third-generation EIA, the yield of HCV lookback was likely zero. Because HCV infection is relatively common in the general population and patients in Canada do not undergo pretransfusion testing, coincident infections in recipients may be erroneously attributed to transfusion. The regulatory requirement for HCV lookback should be reassessed.