How does this compare with the repeat reactive rate for the HIV antibody test?
Fewer than five in every 10,000 donors, or 0.05%, test repeat reactive for HIV antibodies. How many of these repeat reactive antigen tests can be expected to be truly positive after they are tested using a more specific confirmatory test called the neutralization test? Over 99% of HIV antigen repeat reactive donors will not have a positive confirmatory test result and will be classified as false positive. Fewer than one of every 300 repeat reactive donors is true antigen positive, or antigen neutralizable. Initial estimates were than one in 1 million donors would be true HIV antigen positive, but negative on the other HIV test used by blood banks, HIV antibody. In fact, one to two donors in the United States per year fall into the window period between antigen test positivity and antibody test positivity. Identification of these donors will shorten the period between time of infectiousness and test reactivity, now estimated at 22 days, by 6 to 10 days. A greater number of HIV antigen t
