Treatment Effects Are Not Totally Explained by CD4 and RNA

Viral Load Testing

By Jules Levin, Executive Director of NATAP

Dr. Coombs displayed a graph of data from Bill O'Brien's VA study (O'Brien et al, NEJM 1995) which indicated that individuals with both an increase in CD4 and a reduction in viral load clinically progressed more slowly than individuals who had neither and individuals who had only a CD4 increase or a viral load reduction. Dr. Coombs said, that looking at combinations of responses to drugs, both immunologic (CD4) and virologic (RNA) markers are more beneficial than looking at one or the other alone. The data from the Upjohn studies support CD4 and viral load together are more predictive.

He went on to say, we still have a lot to learn about what exactly are the factors that define the treatment effect. At the moment, we are trying to understand how much of the treatment effect can be explained by changes in RNA and/or CD4, and it's clear that even together they explain only part of it, but not all of it. Other studies have illustrated that other factors are relevant, such as properties of the virus and other additional properties of the host, that are extremely important in defining the types of response that individuals will experience from changes in viral load alone. So, it is much more complicated than we are currently appreciating, to better understand an individual's response to treatment. At the moment, we are left with more simple markers of the disease, for example CD4 and viral load, to help make clinical decisions about what does or doesn't constitutes effective therapy. In future clinical studies, it would be helpful if we are able to factor in other properties or disease markers.

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About the author: Jules Levin is the Executive Director of NATAP, based in New York City.

The National AIDS Treatment Advocacy Project (NATAP) is a New York State non-profit corporation dedicated to facilitating the effort for development of effective treatment for HIV.

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