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What every laboratorian should know about AIDS.

What every laboratorian should know about AIDS

The 10 to 12 million units of blood given to 3.5 million patients every year in the United States carry many potential hazards, including mismatches, sensitization, and the most common danger, infection. Yet the most feared hazard of all--the transmission of AIDS--is now among the least likely to occur.

Nationwide, the odds of a transfused patient dying from transfusion-associated hepatitis are more than 1,000 times greater than the odds of dying from transfusion-associated AIDS. Virtual elimination of the paid blood donor and use of hepatitis B vaccine and antibody tests have almost eliminated hepatitis B as a hazard. Post-transfusion hepatitis persists at a rate of 7 to 10 per cent of transfusion cases because 80 to 90 per cent of those cases are the non-A, non-B variety, for which there is no test.

Even before the ELISA test for antibodies to HTLV-III, the incidence of transfusion-associated AIDS reportedly fell from 1 in 100,000 to 1 in 1,000,000. With the ELISA test mandatory in blood banks, the incidence should drop further, although it may take years to see the effect because of the virus's long incubation in patients infected before the blood test.

Part I of this report (MLO, November) noted that 2 per cent of AIDS cases have been linked to transfusions--236 cases as of Sept. 30, 1985, with 210 in adults and 26 in children. In San Francisco, the rate of transfusion-associated AIDS was 50 times the national rate. Prior to ELISA testing, patients transfused with blood from centers in that city and in metropolitan New York, Los Angeles, or Miami were probably at higher risk for infection. But since blood supplies cross state lines, no area has been completely safe.

Before they had the HTLV-III antibody test, some blood banks screened donated blood for hepatitis B core antibody to lower the AIDS risk in blood supplies.

Hepatitis B and AIDS are totally different diseases caused by totally unrelated viruses, but it has been shown that persons whose life-style puts them at high risk for AIDS probably have also been exposed to hepatitis B. For similar reasons, some blood banks tested for Epstein-Barr virus and cytomegalovirus. Others screened for T-cell subsets and helper/suppressor cell ratios.

Blood banks also began "social screening' by clinical history in May 1983. Members of AIDS risk groups are asked not to donate. Under U.S. Public Health Service guidelines, blood or plasma should not be donated by persons with signs or symptoms of acquired immune deficiency syndrome, sex partners of AIDS patients or those at high risk of AIDS, males who have had even a single homosexual experience since 1977, past or current abusers of intravenous drugs, and hemophiliacs.

Today, the ELISA test for HTLV-III antibody is the blood bank's best tool for maintaining the safety of the blood supply. (It is also used for epidemiologic studies on at-risk populations.) Of more than 3 million units collected at 75 regional Red Cross blood centers through September 1985, 0.2 per cent were reported repeatedly positive and discarded. Of the positive units, however, only 0.04 per cent could be confirmed by the Western blot test, constituting a potential false-positive rate of 0.16 per cent.

Although the ELISA test has, in effect, eliminated the AIDS risk in transfused blood, no one knows exactly how to interpret the results in individual patients: It is not a test for the AIDS-related complex (ARC), AIDS, or future disease, although a positive reaction indicates that a person has probably been infected with HTLV-III.

The test occasionally yields false-negative as well as false-positive results. Because donors may be infectious for months before seroconversion, an assay for viral antigen will probably be necessary to complete an AIDS screen.

A positive test seems to indicate greater chance of infection and infectivity. The Center for Disease Control reports that 5 to 10 per cent of gay men positive for three years develop AIDS. The safe course is to assume that once infected, even an asymptomatic patient remains infected and infectious for life.

Initial studies show that the ELISA test is 99.8 per cent accurate. Of the less than 1 per cent of blood donors who test positive, almost three-quarters are not confirmed as positive in repeat testing and by the Western blot test, a less sensitive but more specific procedure.

An ELISA-positive unit of blood must be discarded, the donor informed, and his or her name placed on a "donor deferral' list that bars any future donations.

This policy raises several questions: Should test results be accessible, and if so, to whom? Or should they be kept secret?

Advocates for some high-risk groups insist that results should be confidential. They argue that if positive results, including false ones, are publicized, the donor will not only have to cope with the possibility of AIDS, but may also be denied health or life insurance, face a loss of employment, be refused a marriage license, and, most important, have to alter personal behavior for a lifetime to avoid spreading the infection to friends and family.

Problems with the ELISA test in blood banks don't end there. Members of high-risk groups may offer to donate blood only to determine if they have been exposed to HTLV-III. Those with false-negative reactions will be accepted as donors, further contaminating blood supplies. Discouraging such abuse by refusing to disclose results to the donor would be doubly counterproductive. The donor might try to donate a second time to see if his or her name has been placed on the list of unacceptable donors.

California and the CDC are responding by establishing local alternative testing centers, not associated with blood banks, where high-risk individuals can take the ELISA test anonymously and at no cost.

In California, enabling legislation for these centers forbids disclosure of results without the patient's written permission. If the patient suffers mental anguish, physical harm, or financial loss as a result of unauthorized disclosure, responsible parties can be fined up to $10,000, jailed for as long as two years, or both.

This is an unfortunate step. Perhaps members of the public should be alerted in their dealings with certain kinds of AIDS victims. True, AIDS doesn't appear to spread by food handling or casual contact, but nondisclosure laws may jeopardize those receiving the services of AIDS-infected physicians, nurses, dentists, opticians who fit contact lenses, firemen who perform cardiopulmonary resuscitation, nursery school workers, barbers, and so on. In addition, if a physician warns colleagues, nurses, or medical technologists to take appropriate AIDS precautions with a patient, that could be construed as unauthorized disclosure.

Some patients have turned to directed donations as a means of protecting against transfusion-associated AIDS. These patients, anticipating the need for transfusion, entreat family and friends to donate blood specifically for their use, hoping to diminish the risk of contamination. They are misguided. With the possible exception of family with whom the patient lives, we have no evidence that directed blood donations are safer than blood from the community pool.

First-time donors provide as much as 90 per cent of directed donations, whereas 85 per cent of volunteer donations are from repeat donors. Blood from repeat volunteers is tested not only in the laboratory, but also biologically, because their previously donated blood has not caused acquired immune deficiency syndrome or hepatitis in other recipients.

In addition, directed donors are under pressure to donate. That might cause them to conceal information about exposure to hepatitis, homosexual activity, infection, or medications they are taking.

Irwin Memorial Blood Bank in San Francisco reports that its incidence of HTLV-III-positive blood is comparable in voluntary and directed-donation blood. For all of these reasons, the American Red Cross, the American Association of Blood Banks, and the Council of Community Blood Centers have discouraged the practice of directed donations.

Directed donors often don't realize that by forgoing usual donor confidentiality they are open to legal action if the recipient suffers injury from transfusion.

The patient who donates blood for his or her own use at subsequently scheduled surgery takes a far safer and more effective step to avoid transfusion-associated infections and other problems. Unfortunately, many candidates for surgery aren't informed by their surgeons of this option.

No transfusion is safer than an autologous one. The best testimony is that physicians and their families exercise this option frequently --and did so even before AIDS. Mismatching, sensitization, allergic reaction, hepatitis, AIDS--all are eliminated.

Autologous transfusion can't be used for medically indicated transfusion or to meet unanticipated needs, such as blood loss due to trauma. But most surgical procedures are scheduled, if not elective, and then there is ample time for the autologous donation.

Modern practices permit the patient to stockpile five or six units easily and safely. Because blood can be stored for five weeks, the patient can donate at a comfortable rate of one unit every five to seven days, up to three days before surgery. Two or three units are generally enough for most surgical procedures.

The Kaiser-Permanente Medical Center in Santa Clara is the largest user of autologous blood in northern California, thanks to patients' informed participation and the active cooperation of surgeons. We use 50 per cent of the autologous blood drawn by the Central California Red Cross Blood Bank, which supplies 25 hospitals. In 1984 that was 7 per cent of our transfusions, a record we hope to double in 1985. Some 165 patients donated almost 300 autologous units and used 60 per cent of it with no adverse reactions. Most unused blood was returned to the Red Cross for other patients.

An autologous donation and transfusion program can work as well for your patients as it does for ours. If your medical center does not have such a program, find out why and work toward a change.

Let us, in concluding, briefly assess the cost of AIDS. Approximately 10 per cent of AIDS patients are hospitalized at any given time. The CDC estimates that the average lifetime hospitalization cost for an AIDS patient is $140,000, although the San Francisco Department of Public Health estimates it is between $50,000 and $62,000.

Nationally, the medical bill will probably exceed $1.5 billion in 1985, including about $100 million to screen blood donors. A key question is: Where should all that money come from?

AIDS also exacts a high death toll and emotional costs. For patients, there are rising and falling hopes, isolation, and suffering. People at high risk face lifelong uncertainties and fears. Families and friends share the burden, and those who treat AIDS patients can be devastated by the relentless destruction of young, intelligent, productive lives.
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Title Annotation:HTLV-III testing
Author:Haber, Seth L.; Becker, Brenda L.
Publication:Medical Laboratory Observer
Date:Dec 1, 1985
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