Date: Fri, 14 Jun 1996 00:33:44 -0400 From: "Flynn Mclean" Subject: CDC National AIDS Hotline Training Bulletin #172 ................................................................. CENTERS FOR DISEASE CONTROL AND PREVENTION HIV/AIDS PREVENTION CDC NATIONAL AIDS HOTLINE TRAINING BULLETIN ................................................................. March 20, 1996 #172 This is a statement from the Centers for Disease Control and Prevention (CDC) concerning testing and counseling blood and plasma donors for human immunodeficiency virus type 1 antigen: Guidelines of the U.S. Public Health Service, as published in the March 4, 1996, MMWR Reports and Recommendations A multifaceted approach implemented by the U.S. Public Health Service (PHS) ensures the safety of America's blood supply. A larger number of and more sensitive laboratory screening tests, coupled with careful donor questioning to defer high-risk donors, have almost completely eliminated the risk of HIV infection through blood transfusion in this country. Blood donations in the United States have been screened for antibody to HIV-1 since March 1985 and HIV-2 since June 1992. HIV antibody tests indicate HIV infection, but do not directly detect the virus. The body usually begins making antibodies within days of HIV infection. Usually, enough antibodies are made within several weeks to be found by an antibody test. The period when infection is not detected by an antibody test is known as the "window period." To shorten the window period and make the blood supply even safer, the Food and Drug Administration (FDA) has recommended that blood banks and plasma centers add a test for p24 antigen to their screening. The p24 antigen is a core protein in HIV. On average, the p24 antigen is detected about a week before antibody tests become positive. Once HIV antibody becomes detectable, the p24 antigen test often becomes nonreactive, because all the p24 in the blood combines with HIV antibody. Because of screening procedures already in place, only 18-27 units of blood out of the 12 million units donated each year are calculated to carry HIV. The antigen test is expected to reduce that number by approximately 25% (4-6 donations) per year. Antigen Test Not Recommended As Routine Diagnostic Tool for Individuals CDC does not recommend the p24 antigen test for routine use in HIV counseling and testing sites. Guidelines for counseling and testing individual patients already take into account the window period and recommend follow-up antibody testing. Antigen testing detects HIV infection only a few days before antibody testing does. And the time in which the antigen can be found is very short--once antibodies are detectable, antigen is often not detectable. Antibody testing at the recommended intervals is the best way for health care providers to routinely diagnose HIV in individual patients. Counseling and Follow-Up Testing Essential As blood banks and plasma centers prepare to implement this additional testing, PHS has issued guidelines to help them interpret results and provide counseling and follow-up testing for people whose results are either positive or indeterminate. Follow-up will be critical, because about 1 in 2,000 initial screening test results are expected to be "false positives." Because HIV infection among blood donors is already extremely rare, and the blood supply is already so safe, most blood donations that initially screen positive will, in fact, be false positives. To reduce the chance that an HIV-infected donation would be missed, the p24 antigen test has been designed to detect as many HIV-infected donations as possible. The p24 antigen test reveals a true positive on the very limited number of days when a person has enough antigen to be detected, but not enough HIV antibodies to be detected. Initial counseling will have to make clear that a positive or indeterminant antigen test will have to be followed by an antibody test to confirm HIV infection. Later counseling must provide donors who are confirmed HIV positive by antibody testing with information about other needed tests; referrals to medical, preventive, and psychosocial services; and education about how to prevent transmitting HIV to others (for example, sexual partners). People at risk for HIV infection should not donate blood. Those who want to know their HIV status should seek counseling and testing at sites that use antibody testing to determine HIV infection. Disclaimer: CDC Hotline Training Bulletins The information in the "CDC Hotline Training Bulletins" is provided by CDC and NIH for use by the CDC National AIDS Hotline in responding to general questions from the public about HIV and AIDS. The bulletins are not intended to be comprehensive discussions of the subject areas. Treatment and drug therapy options change as new research and clinical experiences broaden scientific knowledge. Therefore, persons seeking information on drug therapy should refer to the product information sheet included in all drug packages for the most current and accurate information about a particular drug, especially if the drug is new or infrequently used. HIV-infected individuals should consult their personal physician for specific concerns about their health. For persons desiring more information on a specific topic, public, medical, and university libraries can provide excellent references. The AIDS Clinical Trials Information Service (800-874-2572) can provide information about ongoing HIV/AIDS clinical trials; the HIV/AIDS Treatment Information Service (800-448-0440) can assist with information about the latest treatments for persons with HIV infection or AIDS.