The odds of being infected with the deadly AIDS virus through a blood transfusion are "extremely low," even in cities where high-risk populations are prevalent, researchers say.
The first large-scale test of blood supply safety in a major American city found the risk of receiving blood infected with the human immunodeficiency virus - HIV - was one in 61,000 in San Francisco, said Girish Vyash of the University of California at San Francisco.Vyash, director of the university's transfusion research group, said the study "gives us the first very accurate picture of what the risk actually is. It should be reassuring to doctors and patients because now they have not just an estimate but a real number."
Estimates of the risk of aquiring HIV through a transfusion have ranged from one in 40,000 to one in 300,000, depending on where the blood is collected.
Because San Francisco has one of the highest rates of HIV infection of any city in the country, the risk of transfusion-related HIV transmission probably is significantly higher there than in many parts of the country, said Vyash, co-author of the study published in The New England Journal of Medicine.
The study said that with blood that has been routinely screened for HIV - as all donated blood has been in the United States since 1985 - the likelihood of HIV transmission through transfusion "even in high-prevalence metropolitan areas is extremely low."
Vyash and co-researchers formulated their risk estimate after using two types of assays to test blood collected at a San Francisco blood bank. The assays were more sensitive, as well as more time-consuming and expensive, than standard HIV-screening tests, he said.
The blood, from 70,000 donors, had already been screened and was thought to be free of HIV. Vyash said his tests found only one instance of HIV-infected blood that had escaped detection in the initial screening.