KEEPING A SAFE BLOOD SUPPLY
An Overview of Efforts to Protect Transfusion Recipients from HIV
FDA approval of the COULTER™ HIV-1 p24 Antigen Assay, marks a significant advancement in efforts to protect the nation’s blood supply and the estimated four million Americans who receive transfusions each year. While ensuring the purity of transfused blood has always been critical, the rapid spread of the lethal AIDS virus (Human Immunodeficiency Virus type 1) over the last decade has intensified this need. The complicated nature of HIV has also increased the challenges associated with maintaining a safe blood supply.
Blood centers first began screening for HIV in 1985 and have since made great progress in reducing the risk of infection through transfusion. The screening methods used then and today detect antibodies that form in response to HIV. The most widely used tests, ELISA (Enzyme-Linked Immunosorbent Assay) & the Western blot, are considered to be more than 99 percent accurate. However, there is a period of time right after infection during which the HIV antibodies of an infected donor may not appear and therefore would not be detected by these tests. A study reported last year estimated this “window period” to be about 22 to 25 days. Because of the window period, it is also estimated that approximately 41 transfusion recipients in the U.S. become infected with HIV each year.
Rather than screening for HIV antibodies, the p24 test identifies the core antigen of the virus that causes AIDS. Antigens are substances in the blood that the immune system considers foreign and that trigger the production of antibodies. Within the AIDS virus, the most widely recognized antigen is a protein called p24. Experts assert that screening donor blood for HIV antigens reduces the current testing window period by about six days, or approximately 25 percent, and could prevent five to ten of the 41 cases of infection that may result from transfusion each year.
The FDA approved the use of HIV antigen testing in 1989, although not for routine donor screening. At the time, there were no known cases in which donor blood tested negative for HIV antibodies but positive for HIV antigens. Since then, however, four such cases have been documented, prompting the FDA to reconsider its decision.
In 1994, momentum began to build around the idea of donor screening for HIV-1 antigens, as the scientific community continued looking for ways to lower the risk of spreading HIV through transfusion. After further scrutiny of potential public health benefits, the FDA recommended in August 1995 that all blood establishments begin donor screening for HIV antigen within 90 days after a screening test is licensed and approved.
Editors Note: The American Association of Blood Banks, whose members collect virtually all of the nation’s blood supply reports 14 million units of blood are donated annually in the United States. Almost half of that is collected by the American Red Cross, with the remainder coming through community - and hospital-based blood banks.
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