The Bay Area Reporter - February 6, 1996
Matthew Sharp, ACT UP/Golden Gate Writers' Pool

The viral load test is done by two methodologies: the branched DNA test, made by Chiron in Emeryville, and the RNA Polymerase Chain Reaction or RNA-PCR developed by Roche (among other companies). The test counts HIV-RNA copies in blood samples through sensitive techniques.

There is still debate about what the numbers mean - about what constitutes a "good" reading, for example - but it is clear that monitoring their rise and fall can be predictive and guide treatment decisions. Individually and in clinical trials, the test can show whether a treatment is having an effect on the spread of HIV.

The PCR assay is more sensitive, but probably less reliable. At the present time the bDNA is anywhere from $150-$200 retail per test, and the PCR is considerably less at $90-$150 retail. The two tests have not been compared, so their numbers don't necessarily correlate.

At the recent Conference on Retroviruses and Opportunistic Infections in Washington D.C., new viral load data confirmed what researchers and clinicians have been saying: if you can get the viral load down, people live longer. Last week stories in major newspapers across the country indicated that counting HIV-RNA copies in the blood may be the most accurate gauge of HIV disease progression we have.

Useful Test in Trials

Prior to its current widespread use, the viral load was shown to be a useful test in clinical trials of anti-retroviral drugs. In a previous Writers' Pool article, the AIDS Clinical Trials Group ddI studies (ACTG 116B-117) were cited, which showed the effectiveness of the test. Since then confirmations of the usefulness of viral load are coming from Pharmacia & Upjohn's delavirdine studies. 1,900 patients were enrolled in two studies that compared delavirdine plus ddI vs. ddI alone, and in the second trial, AZT vs. delavirdine. The studies also compared clinical outcome to the surrogate markers (laboratory indicators of disease progression), which include viral load. In these studies viral load did a better job of predicting who would die or develop AIDS-related infections than did CD4 count, which until now has been the standard surrogate marker. Counting copies of viral RNA in the blood would seem to make more sense than the indirect effect of the virus on immune cells such as CD4s.

One of the investigators in the delavirdine study, Dr. John Phair, stated in a press release, "These results suggest the threshold level of viral burden which, when reached by anti-retroviral therapy, may delay progression to AIDS illnesses and death. Physicians, patients, and payers will have more confidence that therapy choices are working."

Dr. Bill Owen, a local HIV physician who uses the viral load extensively in his practice, believes "The viral load is not only important for making treatment decisions, but is important to determine if a patient is clinically stable and therefore helps in making a decision not to treat them."

Dr. Marcus Conant, a nationally recognized Bay Area HIV doctor, is taking it a step further by ordering the PCR test in his practice. He states that "the technology is equally good for both tests; Chiron needs to get its second generation [more sensitive] test on the market and make it more available."

But Who's Gonna Pay?

The biggest issue regarding viral load is not whether it works, but whether people with AIDS can access the test.

In mid-America viral load tests are simply not available, due to inadequate laboratories. Although physicians can send blood samples away, the cost incurred can add up. Dr. Aline Brown, an infectious disease doctor in Oklahoma City, doesn't use the tests because of their inaccessibility. In the Bay Area, where tests are available, some HMOs like Kaiser Permanente are reluctant to pay, no matter how overwhelming the evidence or how much the demand. They choose to wait until the bureaucratic, snail-paced FDA sanctions the test. (According to Conant, the same Kaiser wouldn't pay for CD4 testing before its approval in the mid-eighties.)

Getting that FDA approval of this type of surrogate marker can be problematic. However, for the first time we are seeing proof in large trials that may speed the tests' authorization. A University of Pittsburgh study followed 181 patients for ten years and found in those with lower viral loads the onset of AIDS was in eight years; for those with higher viral loads, the progression to AIDS was in 6.5 years; and in other even higher viral loads, the time to development of AIDS was 4.5 and 2.5 years respectively.

According to Owen, the application for the bDNA has been "fast tracked" by placing it in the "devices" category. The delavirdine and Pittsburgh studies strongly confirm what is already known about viral load, so - barring a government shutdown - we may see approval by this summer. When approval comes, and marketing brings the costs down, Kaiser will have no choice but to pay.

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