Reduction of the risk of transfusion‐transmitted viral infection by nucleic acid amplification testing in the Western Cape of South Africa: a 5‐year review

Background and Objectives In October 2005, individual donation nucleic acid amplification testing (ID‐NAT) for HIV, HBV and HCV was introduced in the Western Cape Province of South Africa. After 5 years, the impact on HIV, HBV and HCV transmission risk was assessed. Materials and Methods A total of 649 745 donations were tested by ID‐NAT using the Ultrio assay on the Tigris instrument (Novartis Diagnostics) and for anti‐HIV, HBsAg and anti‐HCV (Abbott Prism). Initial reactive samples were repeated in duplicate. Discrepant repeat reactive samples were subjected to confirmatory assays. ID‐NAT nonrepeat reactive donations were further screened for occult HBV infection (OBI) by anti‐HBc assay. Results ID‐NAT yielded 6 HIV‐RNA‐positive donations in the anti‐HIV‐negative window period (WP) but only 2 were p24 Ag nonreactive (1:325 000). Mathematical modelling estimated a similar HIV transmission risk for lapsed and repeat donations, in the order of 3 per million. The WP risk for HBV was 13 per million. Eight acute (1:81 000) and 13 chronic OBI yield cases (1:50 000) were interdicted. There were significantly more anti‐HBc‐positive donors in the Ultrio initial reactive/nonrepeat reactive group (12%) than in an Ultrio nonreactive control group (6%). Conclusion ID‐NAT in the Western Cape Province of South Africa has contributed significantly to enhancing blood safety, particularly for HBV transmission risk and to a lesser extent for HIV. Anti‐HBc testing of NAT nonrepeat reactive donations seems useful in identifying a subgroup of donors with OBI who may be at risk of transmitting HBV.