U.S. Public Health Service guidelines for testing and counseling blood and plasma donors for human immunodeficiency virus type 1 antigen.

The Public Health Service (PHS) has recommended a multifaceted approach to blood safety in the United States that includes stringent donor selection practices and the use of screening tests. Blood donations in the United States have been screened for antibody to human immunodeficiency virus type 1 (HIV-1) since March 1985 and type 2 (HIV-2) since June 1992. An estimated one in 450,000 to one in 660,000 donations per year (i.e., 18-27 donations) are infectious for HIV but are not detected by currently available screening tests. Because maintaining a safe blood supply is a public health priority, the Food and Drug Administration (FDA) recommended in August 1995 that all donated blood and plasma also be screened for HIV-1 p24 antigen, effective within 3 months of licensure of a test labeled for such use. Donor screening for p24 antigen is expected to reduce the number of otherwise undetected infectious donations by approximately 25% per year. Routine testing for p24 antigen in settings other than blood and plasma centers as a method for diagnosing HIV infection is discouraged because the estimated average time from detection of p24 antigen to detection of HIV antibody is 6 days, and not all recently infected persons have detectable levels of p24 antigen. Among children > or = 18 months of age and adults, diagnostic testing for HIV infection, including confirmatory testing, should routinely be performed with FDA-licensed assays for antibodies to HIV-1; p24-antigen tests alone should not be used for diagnosing HIV infection. This report provides PHS guidelines for a) interpreting p24-antigen-assay results, b) counseling and follow-up of blood donors who have positive or indeterminate p24-antigen-test results, and c) using p24-antigen testing in settings other than blood banks.