A new strategy for estimating risks of transfusion-transmitted viral infections based on rates of detection of recently infected donors

BACKGROUND: Estimates for human immunodeficiency virus (HIV)‐1 and hepatitis C virus (HCV) transfusion‐transmitted risks have relied on incidence derived from repeat donor histories and imprecise estimates for infectious, preseroconversion window periods (WPs). STUDY DESIGN AND METHODS: By use of novel approaches, WPs were estimated by back‐extrapolation of acute viral replication dynamics. Incidence was derived from the yield of viremic, antibody‐negative donations detected by routine minipool nucleic acid testing (MP‐NAT) of 37 million US donations (1999‐2002) or from sensitive/less‐sensitive HIV‐1 enzyme immunoassay (S/LS‐EIA) results for seropositive samples from 6.5 million donations (1999). Incidences and WPs were combined to calculate risks and project yield of individual donation (ID)‐NAT. RESULTS: The HIV‐1 WP from presumed infectivity (1 copy/20 mL) to ID‐NAT detection was estimated at 5.6 days, and the periods from ID to MP‐NAT detection and from MP‐NAT to p24 detection at 3.4 and 6.0 days, respectively; corresponding estimates for HCV were 4.9, 2.5, and 50.9 days (the latter represents period from MP‐NAT to HCV antibody detection). The HIV‐1 incidence projected from MP‐NAT yield or from S/LS‐EIA data was 1.8 per 100,000 person‐years, resulting in a corresponding HIV‐1 transfusion‐transmitted risk of 1 in 2.3 million. The HCV incidence from MP‐NAT yield was 2.70 per 100,000 person‐years with a corresponding risk of 1 in 1.8 million donations. Conversion from MP‐NAT to ID‐NAT was projected to detect two to three additional HIV‐1 and HCV infectious units annually. CONCLUSIONS: MP‐NAT yield and S/LS‐EIA rates can accurately project transfusion risks. HCV and HIV‐1 risks, currently estimated at 1 per 2 million units, could be reduced to 1 in 3 to 4 million units by ID‐NAT screening.