Testing Assures Blood Supply Is Safe From AIDS Virus--Almost

Since the Red Cross and other blood centers began routinely testing donated blood for AIDS virus antibodies in March, 1985, health officials have said that the public need not worry about getting AIDS from a blood transfusion.

But there have been disturbing exceptions.

In the summer of 1985, a 60-year-old man was apparently infected with the AIDS virus from blood he received during surgery. The standard blood test for evidence of AIDS found no sign of the virus in the transfused blood, donated by a Colorado man the previous May.

Although the donor had been infected with AIDS and was carrying live virus in his blood, his immune system had not yet recognized the virus and thus had not developed the antibodies the blood test looks for. When the man donated blood again in November, the test was positive and the blood was thrown out. But in May there was nothing for the test to detect.

Health officials call this the “window period” for AIDS transmission, the time between AIDS infection and when evidence of it shows up in blood tests.

Serious Concern

It is a matter of serious concern for health authorities. Even though tests are being developed to detect the AIDS virus immediately, these tests will not be available for at least a year and may not be sensitive enough for mass screening.

Right now, most experts agree that there is not much to be done about this problem except to discourage people who might be in the AIDS window from donating blood.

“The window period is a fact that we’ve all known since the tests were instituted,” said Dr. Gerald Sandler, associate vice president for medical operations at the American Red Cross. “But we still feel the antibody tests are good tests.”

The blood supply is much safer now than before the antibody tests.

As of September, 624 adults and 62 children had come down with acquired immune deficiency syndrome as a result of receiving untested blood, the federal Centers for Disease Control said. These statistics include hemophiliacs, who because of their disease often receive massive amounts of blood.

In contrast, only two AIDS virus infections--not full-blown cases--have been attributed to the screened blood. The second case, which the CDC has not even officially announced, occurred under circumstances similar to the first, a CDC official said.

But what is not known is how many other infected donors may have slipped through the AIDS window since screening began.

Estimates Called Guesswork

One Stanford University statistician has estimated that one in 100,000 current donations are positive for the virus but test negative, meaning that about 120 of the 12 million pints collected every year are possibly infectious. Other experts criticize that figure as too high, and most say any estimate at this point is just guesswork.

“We really have quite a few more months before we can extrapolate from what we’ve seen to what is actually the case,” Sandler said. “But I think I can say the blood supply is as safe as it can possibly be made.

“Every effort that can be made has been made,” he said. “Our screening method is as intensive and direct as we are capable of doing.”

When someone comes in to donate blood at the Red Cross, they receive a pamphlet that explicitly outlines high-risk behavior for AIDS, such as homosexual activity and the use of intravenous drugs. Those who admit to participating in any of these activities are rejected as donors.

“The window period begins immediately at the moment of risk behavior, and ends a few weeks after that risk behavior,” Sandler said. “If we can increase education and make people thoroughly aware of these risks, we should be able to eliminate the problem.”

Increased Education Credited

To some degree, this has worked. The number of blood units testing positive has dropped from four in 10,000 to one in 10,000 since screening began, a fact Sandler attributes to increased education and the removal of infected donors from the donor pool.

But many people who should know they are at risk still give blood.

“We need to evaluate why some people continue to donate blood when they know they may be at risk for AIDS,” said Dr. John Ward, of the federal Centers for Disease Control in Atlanta.

“Blood donors are not going in for malicious intent,” he said. “They’re certainly not intending to harm anyone, but at the same time they may be at a risk for AIDS and they may not perceive they are at risk.

“I assume that the reasons that it happens are probably not too different from the reasons why people don’t use seat belts or they don’t quit smoking cigarettes,” Sandler said. “They just don’t think it will be them.”

The Colorado donor, for example, first gave blood soon after his first homosexual encounter without condoms in 11 years.

About 75% of the people with infected blood admit to high-risk activity when the Red Cross informs them of a positive test, Sandler said.

‘People Are Shocked’

“Our interviews have shown repeatedly that people are shocked that the one time they took intravenous drugs, or their one dalliance into bisexuality, has resulted in an infection,” he said. “And they are all very sorry they put someone else at risk by donating blood.”

To the extent that some high-risk donors are not abstaining from giving blood, blood centers are doing what they can to avoid getting infected blood, even if it means eliminating entire groups from the donor pool. The Red Cross has announced that it will no longer coordinate blood drives with homosexual groups, or in neighborhoods with a large number of intravenous drug users.

Sandler said he regrets that this policy is necessary, particularly since homosexual groups were very active supporters of the blood program before being identified as high-risk carriers. But, he said, “It’s simply inappropriate to have a blood drive in an area where a number of high-risk individuals have been identified.”

Blood centers still conduct blood drives at churches, community groups and corporations, however, and it is precisely in these situations that a person might choose to donate blood rather than raise questions about homosexuality or intravenous drug use.

Dealing with this problem requires sensitivity and ingenuity, said Dr. Johanna Pindyck, director of the greater New York blood program.

“In addition to asking people not to give blood, which has been a standard protocol, we’ve also given people who have reason to believe they might be at risk the opportunity to only give blood for study purposes,” Pindyck said.

“If someone thinks they might be at risk or for some reason feels compelled to give blood because of the setting, they can tell us they don’t want it transfused,” she said. “And that blood never, ever makes it into our blood supply.”

The Red Cross and other blood centers recognize that despite their best efforts, some people who are infected with the AIDS virus are going to donate, and in some cases, their blood is going to go undetected. They all agree that a better test is the only solution, but few are optimistic that such a test is forthcoming.

The present test, called an enzyme-linked immunosorbent assay, is good at what it does--detects antibodies to HTLV-3, the virus that causes AIDS. The test is in fact so sensitive that it will sometimes register positive when no antibodies are present.

But Dr. Tom Peterman, a CDC epidemiologist, noted, “The antibody test is a test for antibodies, and what you’re really interested in is the virus.”

Efforts to test for the virus are fraught with complications. Most such tests attempt to detect antigens, the parts of the virus that trigger the production of antibodies in a human. Unfortunately, these antigens are usually present in minute quantities, and scientists have yet to duplicate the sensitivity of the human immune system.

“All of the antigen tests that are available right now require a culture step, so that the antigen can be increased in its concentration so it can be detected,” Sandler said. “None of these tests are being considered as screening tests.”