San Francisco Chronicle - Tuesday, June 6, 1989
David Perlman, Chronicle Science Editor

Researchers at the national Centers for Disease Control in Atlanta, at the Irwin Memorial Blood Bank in San Francisco and in several European countries have been testing donated blood for safety with new, advanced techniques.

Yesterday, at the fifth annual International Conference on AIDS, where more than 10,000 researchers and public health workers are gathered, the blood researchers agreed that they are reaching similar conclusions:

Because of improvements in screening donors and testing their blood, the scientists said, there is now less than one chance in 40,000 that a single unit of transfused blood is contaminated with HIV, the human immunodeficiency virus.

A collaborative study of transfusions in 29 European countries, for example, showed that about 3,000 AIDS cases are occurring there as a result of virus-contaminated transfusions performed before the first test for antibodies to the AIDS virus was introduced in 1985.

But according to Dr. Angela M. Downs of the World Health Organization blood study center in Paris, no more cases have been recorded among patients who received transfusions after 1985.

Dr. John W. Ward, a federal medical epidemiologist, reported that as of last month, 2,529 cases of transfusion-associated AIDS had been recorded in America since the epidemic began in 1981. But only four of those cases have occurred since the standard antibody test came into use in 1985, he said.

The antibody test is used in virtually all blood banks throughout the world, and subtle questionnaires are used to eliminate any would-be donors who might be at high risk for infection.

This combination of antibody tests and personal screening is making today's blood transfusions extremely safe, Ward said. "SILENT INFECTIONS'

Last Week, the New England Journal of Medicine published a worrisome report from researchers at the University of California at Los Angeles who claimed that they have detected evidence of a significant number of "silent " AIDS virus infections.

The researchers, led by UCLA's Dr. David Imagawa, said that in a group of 133 gay men who persisted in engaging in extremely high-risk sex activities, nearly one quarter of them had been actively carrying the AIDS virus for as long as three years without any evidence of infection ever showing up in their standard antibody tests.

Some AIDS specialists questioned the evidence; others termed the report extremely depressing.

The so-called silent infections were detected by examining the blood of the gay men and testing their frozen white blood cells using a new technique called polymerase chain reaction, which amplifies the genetic material inside the virus so it can be easily studied.

Researchers at the Irwin Memorial Blood Bank in San Francisco, however, have reached a much different conclusion. Dr. Michael Busch at the nonprofit Irwin bank has just completed tests using the same polymerase chain reaction technique to analyze 45,650 donated units of throughly screened blood, and found only one case where the newly developed technique showed evidence that the virus was present.

Another highly reliable method of detecting HIV infection in blood is the P-24 antigen test. Here the suspected blood cells are cultured, and a highly specific protein called P-24, carried by the virus on its surface, can be detected without error.

Busch and colleagues from the American Red Cross and the American Association of Blood Banks are now using the P-24 antigen test to examine antibody-free blood samples taken from at least 200,000 donations nationwide.

So far, Busch indicated, the project has not revealed a single case of so-called silent infection by HIV.

Even more convincing is a major new study reported here yesterday by blood specialists from the University of Munich and the German Red Cross. Dr. Joseph Eberle of Munich reported that his group has now analyzed more than 620,000 blood samples taken from regular volunteer donors all over Germany.

Every sample, Eberle said, tested negative in the standard AIDS antibody test and also proved to be free of virus infection when it was subjected to the P-24 antigen test.

Always watch for outdated information. This article first appeared in 1989. This material is designed to support, not replace, the relationship that exists between you and your doctor.

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