Important note: Information in this article was accurate in 2006. The state of the art may have changed since the publication date.
BBC News - September 26, 2006
A study involving 2,800 people suggests measuring viral load is a much less reliable way to predict loss of key CD4 immune cells than previously thought.
The finding may lead to a rethink on asssessing when to start treatment.
The study, led by Case Western Reserve University, appears in the Journal of the American Medical Association.
Predicting disease progression is crucial in the treatment of HIV-positive people - in particular the decision about when to start antiretroviral therapy (HAART).
HAART has been credited with saving millions of lives, but it can cause potent side effects, and so doctors do not like to start using it until absolutely necessary.
More complex
Current treatment guidelines advise doctors that measuring viral load can be one way of assessing when to start treatment for some patients - although in the UK actual CD4 count is deemed to be the most important factor.
HIV specifically targets CD4 cells, a type of white blood cell, and as they decline in number the body loses the ability to fight off infection, raising the risk of complications associated with Aids.
The theory is that the higher the viral load, the faster CD4 cells will be lost.
However, the latest study found viral load explains only about 5% of the variation from person to person in the rate of CD4 cell loss.
This suggests CD4 depletion cannot be viewed as a simple consequence of the amount of virus circulating in the blood.
Instead, the findings suggest the factors governing disease progression are rather more complex, and may include damage that HIV is able to inflict on the immune system in an indirect way.
Patient management
Lead researcher Dr Benigno Rodriguez said: "The results of this study may have profound implications in our understanding of how HIV causes disease and in our approach to the management of HIV-infected patients."
The researchers used a sophisticated statistical modeling technique to assess viral load and CD4 cell loss in more than 2,800 patients with HIV who were not receiving treatment.
Edwin Bernard, editor of AIDS Treatment Update, said it was known that CD4 decline varied enormously between people with a similar viral load, and that treatment guidelines had begun to play down the importance of the measure as a diagnostic tool.
"This study provides important new information to help us understand exactly how much viral load can predict the need to start treatment on an individual level."
He said it was clear that a variety of genetic and immunological factors affected an individual's response to HIV infection - and ways to measure these factors would become key.
However, he said the study did not question the value of viral load measurements for assessing how well antiretroviral therapy was working.
Mary Lima, of the HIV charity Terrence Higgins Trust said: "The immune system is very complex, so more research is needed to clarify how the disease progresses and when medication would be most effectively started."
060926
BB060920
Copyright © 2006 - BBC. Reproduction of this article (other than one copy for personal reference) must be cleared through the BBC.
AEGiS is a 501(c)3, not-for-profit, tax-exempt, educational corporation. AEGiS is made possible through unrestricted funding from Boehringer Ingelheim, Bridgestone/Firestone Charitable Trust, Elton John AIDS Foundation UK, the National Library of Medicine, AIDS Walk of Orange County, and donations from users like you.
Always watch for outdated information. This article first appeared in 2006. This material is designed to support, not replace, the relationship that exists between you and your doctor.
AEGiS presents published material, reprinted with permission and neither endorses nor opposes any material. All information contained on this website, including information relating to health conditions, products, and treatments, is for informational purposes only. It is often presented in summary or aggregate form. It is not meant to be a substitute for the advice provided by your own physician or other medical professionals. Always discuss treatment options with a doctor who specializes in treating HIV.
Copyright ©1980, 2006. AEGiS. All materials appearing on AEGiS are protected by copyright as a collective work or compilation under U.S. copyright and other laws and are the property of AEGiS, or the party credited as the provider of the content.
.