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Study Finds HIV Level, Not Immune Cells, Measures AIDS

By Marlene Cimons
Los Angeles Times
WASHINGTON

Scientists reported Tuesday that infected persons with high levels of human immunodeficiency virus develop AIDS much more rapidly than those with lower amounts of the virus, a finding that likely will affect how individual treatment decisions are made.

Addressing the Third Conference on Retroviruses and Opportunistic Infections, researchers said that measuring viral load is a much more accurate predictor of disease progression than the current method of counting CD4 cells, the key immune system cells that are the primary target of the virus.

"Our findings ... can predict disease progression as far as 10 years into the future," said Dr. John W. Mellors, the study's lead investigator. "You can actually define the individual risk of AIDS before it occurs. This gives us a real handle as to where the individual patient is."

The levels of virus should "absolutely" have "more weight" in assessing a patient's prognosis than gauging the strength of the immune system through CD4 levels, Mellors said.

"You can actually see a doubling of (viral) levels at least two years before you see a 100 cell decline in CD4 levels," he said. It is viral reproduction that ultimately depletes CD4 cells, leading to the destruction of the immune system.

In the largest study of its kind, researchers at the University of Pittsburgh Medical Center used a new test developed by Chiron Diagnostics to analyze blood plasma samples collected every six months from 181 HIV-positive individuals over a 10-year period.

They determined that the risk of developing AIDS symptoms after seven years was less than 10 percent among those with the lowest levels of virus. On the other hand, 60 percent of those with the highest viral load progressed to AIDS.

Viral load measurement also proved to be an accurate predictor of survival. In subjects whose levels were the lowest, none died within five years of the measurement, compared to 65 percent of those with the greatest levels.

While many experts believe that early drug therapy ultimately will be the most effective strategy against AIDS, they also stress that treatment should be tailored to each patient.

Using an analogy to cancer, Mellors urged clinicians to "stage" AIDS by measuring viral load, rather than CD4 counts, to determine how quickly a patient is likely to develop AIDS.