San Francisco Chronicle - Tuesday, November 10, 1992
Sabin Russell, Chronicle Staff Writer

The study by USC researchers Dr. James Mosley and Marek Nowicki was presented at the American Association of Blood Banks' 45th annual meeting this week in San Francisco.

"We were quite surprised by the results," Mosley said in a telephone interview.

Although the study provides reassuring news about the ability of today's tests to screen blood for signs of the AIDS virus, it also raises unsettling questions about the effectiveness of the tests taken six years ago.

Mosley said the suspect test used in the early studies was used by about one-third of the nation's blood banks before a new and more sensitive test replaced it.

AIDS tests detect antibodies formed by the body to fight the human immunodeficiency virus, which causes AIDS. They first became commercially available to blood banks in March 1985.

The USC researchers drew 1,500 samples from a bank that is storing 200,000 blood specimens taken from donors in 1984 and 1985, before the first AIDS test was commercially available. The stored samples were first given an AIDS test for an epidemiological study in 1985 and 1986; at that time the 1,500 samples yielded eight positives.

Six years later, Mosley's group retested the same samples with the more sensitive screen in use today and found eight more positives -- double the number detected with the early test. "What this shows is that the tests we used initially were not nearly as good as the tests we have at the present time," Mosley said.

The researcher noted that the 1,500 samples used in the study were drawn from donors in Miami, where there were large numbers of injection drug users and AIDS infection rates at the time were the highest in the nation. Because people in this group were becoming infected so quickly at the time the blood samples were taken, the group may have had a disproportionate number of subjects whose blood was infected but just below the threshold of the earlier test.

Mosley said it would be a massive undertaking and would cause unnecessary alarm to attempt to reach the 200,000 whose blood was screened in the initial test. "Anyone with a false negative in 1984 probably has a manifestation of disease by 1992," he said.

He said it is not uncommon for blood screening tests to improve with time. Within two years of the introduction of the initial test, better versions were on the market. "It has been a gradual process of improvement," he said.

Dr. Shannon Cooper, president of the American Association of Blood Banks, said he saw a favorable message in the USC research. "Clearly, the tests are much better now," he said. He added that the original test, which appears to have missed so many cases of HIV infection, "was not in widespread use in blood banks."

Dr. Herbert Perkins, president of San Francisco's Irwin Memorial Blood Bank, said he expected to hear of a few false negatives but was surprised that half the infections were missed by the early test. "There is no question that the tests today are more sensitive," he said.

Since the days when the blood samples used in this study were drawn, blood banks have instituted tough screening criteria to dissuade people at high risk for AIDS from donating blood in the first place, and more accurate tests are available to catch any infected blood that slips through the initial screen.

"We now have the safest blood supply by far that this world has ever seen," Perkins said.

Delegates to the blood bank convention yesterday were assured that the chances of tainted blood getting through the system today are vanishingly small: about one in 225,000. Copyright 1992 The San Francisco Chronicle

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