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FDA Approves First Test for HIV Antigen Screening of Blood Donors

Date: March 14, 1996
Source: Food and Drug Administration (FDA)

The Food and Drug Administration today announced the approval of the first antigen test kit to screen blood donors for HIV-1, the virus that is responsible for the vast majority of AIDS cases in the United States.

Currently, blood donors are screened with tests that detect HIV antibodies, which typically appear within three months after infection and indicate the body is responding to the infection. In contrast, antigens, which are the virus' own proteins, can be detected about one week earlier than antibodies.

The new test kit was also approved to be used as needed in the diagnosis of HIV-1 infection and to monitor the progress of the disease itself. However, while the FDA recommends that the antigen test be used to screen blood donations, the Public Health Service does not recommend that it replace the HIV antibody test for routine patient testing and counseling in a medical setting. Antibody testing at the recommended intervals is still the most efficient way for health care providers to routinely diagnose HIV in individual patients.

This new HIV screening test should increase public confidence in the safety of the U.S. blood supply," Assistant Secretary for Health Philip R. Lee, M.D., said. "For any patient who needs blood, the risk of getting AIDS from a transfusion will be even more remote than before."

By reducing the so-called "window" period, when donors may be HIV-infected but still have negative antibody tests, it has been estimated that HIV-1 antigen screening could prevent approximately 5-10 cases per year or up to 25 percent of current cases of AIDS transmitted by transfusion.

We will never totally eliminate the risk of HIV transmission through transfusion, but we have taken important steps to further reduce what is already a very small risk," said Commissioner of Food and Drugs David A. Kessler, M.D.

The new screening test kit is manufactured by the Coulter Corporation, Miami, Fla.

Based on an Aug. 8, 1995 FDA recommendation to all registered blood and plasma establishments, the Coulter HIV-1 p24 Antigen Assay, or other similar tests that may be approved later, will start being used within 90 days of this first approval. Testing for antibodies to HIV-1 and HIV-2, a type of the virus rarely found in the U.S., will continue to be performed in addition to other recommended safeguards to reduce the chance of HIV-contaminated blood entering the blood supply. Other safeguards include the questioning of potential donors about risk behaviors.

The agency's decision to approve the test kit for donor screening was based on a review of safety and effectiveness data. The Coulter test detected HIV-1 antigen before antibodies were detected in 80.6 percent of the cases studied. Also, the test was able to correctly identify HIV-1 negative specimens 99.95 percent of the time based on evaluations of 301,699 normal blood donations. Although an HIV-1 antigen test kit (HIVAG-1), manufactured by Abbott Laboratories was approved in 1989 for diagnosis and monitoring purposes, it was not approved or labeled for donor screening in blood establishments.

Studies at that time indicated no evidence of HIV antigen-positive, antibody negative blood donations after screening over 500,000 samples. However, since 1989, four cases of HIV-1 infection have been discovered to come from blood donations that were later found to be HIV-1 antigen positive, but were antibody-negative at the time of donation.

FDA has been working closely with the blood industry to minimize the burden of implementing this new screening test for the approximately 14 million blood donations processed annually in the United States.

The Coulter screening test kit will be marketed to blood establishments by Ortho Diagnostic Systems Inc., a subsidiary of the Johnson and Johnson Company, Raritan, N.J.