Background and objectives: Since March 1990, all blood donations in Canada are screened by enzyme-linked immunosorbent assay (EIA) for antibodies to HCV, with confirmatory testing done using a recombinant immunoblot assay (RIBA). Because HCV may cause chronic asymptomatic hepatitis, in 1995, the Canadian Red Cross began targeted HCV lookback studies on all confirmed positive donations. These have been continued by the two new operators of the blood system in Canada, Héma-Québec and the Canadian Blood Services. Subsequent to recommendations made in the public inquiry into the Canadian blood system, led by judge Krever, general lookback through letter notification of all patients transfused in the years prior to the introduction of anti-HCV testing was initiated in several pediatric hospitals, and later in several Canadian provinces.
Materials and methods: Targeted HCV lookback was done for all donors confirmed positive by RIBA testing from the start of HCV testing in 1990. In 1999, stored RIBA 2 indeterminate samples were re-tested by RIBA 3, and lookback performed on confirmed positive donations. In the province of Quebec, hospitals were surveyed to determine methods and resources involved in lookback. Provinces performing general letter notification entered hospital transfusion records into a central transfusion data bank, and performed linkage with other provincial data banks to remove deceased patients and obtain current addresses.
Results: As of January 2000, targeted lookback had been completed on 4,859 components of 1,628 anti-HCV positive repeat donors. 2,991 recipients were deceased, and 451 were not found or tested. Of the 1,422 recipients tested, 954 (67%) were anti-HCV positive. Approximately half were already aware of their HCV status. Lookback efforts in hospitals were hampered by lack of resources and manual records. General letter notification in British Columbia (BC) and Prince Edward Island (PEI) led to the testing of 38,960 and 1,953 recipients respectively, with 5.0 and 2.2% of tested recipients found to be anti-HCV positive.
Conclusion: In completed targeted lookback investigations, 19% of components are eventually linked to an anti-HCV positive recipient. These results are very similar to those obtained in other countries, such as Denmark and the UK. In general letter notification lookbacks, the frequency of anti-HCV in the tested recipients is approximately twice the frequency of the general population.