How Accurate is the HIV Test?

By Celia Farber
Mothering Sept./Oct. 1998

People often discuss the dreaded "AIDS test" as though it is AIDS itself that is being tested for. It is not. What the "AIDS test" actually detects is antibodies to HIV, which may or may not entail true infection with HIV. (1) Traditionally, antibodies have signaled that an infection has been defeated. In AIDS, however, for reasons that remain unresolved, the antibody has come to be synonymous with bad news -- a categorical signal that the person "has" HIV and perhaps even "has" AIDS.

Rarely, if ever, has a single diagnostic test had such an enormous impact on the lives of the millions of people who rely on it. Since 1985, the U.S. government and various civilian institutions have performed more than 20 million HIV tests every year. Responses to positive tests have been melodramatic. People have been known to commit suicide or murder, lapse into depression, have abortions, become divorced, and take toxic medications. (2) Tragically, these dramatic actions were triggered by a test that is far from foolproof.

In 1993, a group of Australian researchers published what would be the first substantial critique of the HIV antibody test. The article, entitled "Is a Positive Western Blot Proof of HIV Infection?" was published in the journal Bio/Technology, a respected scientific publication affiliated with the British magazine Nature. The Australian researchers stated that the HIV test is seriously flawed on several counts: it is not standardized, so different labs will interpret the same results differently; it is not reproducible (the test fails when tested against itself); it cross-reacts with other, non-HIV proteins; and it lacks a true "gold standard." Every diagnostic test must have a gold standard, which in this case would be HIV itself, but the authors argue this is impossible since the HIV virus has never been isolated in pure form. (3)

The scientists scrutinized the two most widely used HIV antibody tests -- the "ELISA," which is used to screen blood, and the "Western Blot" (WB), which is used to confirm a positive result on the ELISA. The problems apply to both tests.

The ELISA test, first developed in 1985, is highly sensitive and also extremely nonspecific, which means it gives a positive result even when there is no HIV present. As many as four out of five ELISA tests cannot be confirmed by Western Blot, (4) and yet it remains the most widely used test in the Third World, most notably Africa, where HIV is said to be rampant.

Citing the data from a mass HIV testing program undertaken by the U.S. military, the Australian researchers revealed some startling findings. There were, for instance, 4,000 people who had two positive ELISAs followed by a negative WB. Perhaps worse, there were 80 cases of people who had two positive ELISAs, a positive WB, followed by a negative follow-up WB.

In other words, those 80 people, outside the context of this study, would have gone home believing they were HIV positive, since a single positive WB qualifies a person as positive. But in fact they were negative.

Another problem with the test is that it is nonspecific. The test looks for patterns of proteins thought to be specific to HIV. One protein in particular, p24, is "currently believed to be synonymous with HIV isolation and viremia," the study says. But the Australian researchers detected p24 antibodies in a number of people who were completely free of HIV, including one out of every 150 healthy people, about 13 percent of all people with generalized warts, and more than 40 percent of those with multiple sclerosis. On the other hand, they point out, p24 is not found in all AIDS patients.

But perhaps most troubling, the tests tend to cross-react with other microbes. The Bio/Technology articles describes a tribe of Amazonian Indians who have never had contact outside their tribe and who have no AIDS. And yet, 3.3 to 13.3 percent were HIV- positive by Western Blot. "The above data," they speculated in their final report, means either that HIV is not in fact causing AIDS, "or, that the HIV antibody tests are non-specific."

The test's greatest failing in the eyes of those who've had to rely on it, however, is that it is not standardized. In the Australian study, one particular blood sample was sent 89 times to three different labs. It was reported to be positive 64 times, indeterminate 23 times, and negative once. There is such a broad, gray, "indeterminate" zone, in fact, that it's often merely chance whether a given lab reads the result as positive or negative.

Christine Maggiore, president of the dissident AIDS-activist group HEAL in Los Angeles, experienced this first-hand. After initially testing HIV-positive, and going into the emotional tailspin that such a result often sets off, she subsequently repeated the test four more times, and got every possible result on the spectrum -- positive, negative and indeterminate. "This is why I tell people not to take the test," she says emphatically. "It's just too unreliable. It shouldn't be how we measure our health." *

Celia Farber has written on the issues and controversies surrounding HIV, AZT, and AIDS for more than a decade. She is a regular contributor to Esquire, Spin, USA Today, and Gear, among other national publications. She is the mother of one son and resides with her family in New York City.

Notes:

1. P. Duesberg, Inventing the AIDS Virus (Washington, D.C.: Regnery Publishing, 1996), 207-209.

2. J. Shenton, Positively False, 53-73.

3. E. P. Papadopoulous-Eleopulos and V. Turner, "Is a Positive Western Blot Proof of HIV Infection?" Bio/Technology (2 June 1993): 696-707.

4. R. Root-Bernstein, Rethinking AIDS (New York: Free Press), 51.