Evaluation of a confidential method of excluding blood donors exposed to human immunodeficiency virus.

A confidential self-administered questionnaire was given to all donors prior to blood donation (n = 95,917). The questionnaire describes acquired immunodeficiency syndrome (AIDS) high-risk groups and requires the donor to designate his blood for either laboratory purposes or for transfusion. Six-hundred and twenty-seven people (0.65%; 78% men) designated their blood for laboratory purposes. In addition to routine enzyme-linked immunoassay (EIA) screening for human immunodeficiency virus (HIV) antibody, all units from the latter group of donors were tested by Western blot (WB) irrespective of the EIA result. An equal number of donor units was selected from those designating their blood for transfusion (age, sex and clinic matched) and these too were tested by WB irrespective of the EIA result. We found that donors designating their blood for laboratory purposes had a 10 times (vs transfusion-designated controls) to 100 times (vs general donor population) greater exposure to HIV. In the laboratory-designated group, an EIA negative donor was WB positive, yielding an estimated EIA false-negative rate of 16 per million. A confidential questionnaire, as described, is a valuable adjunct in ascertaining high-risk blood donors.