Orac on the HIV/viral load paper

Orac has a post up on this new JAMA paper as well. He brings up some better examples than the one I gave:

Does anyone in this day and age still believe that smoking doesn’t cause lung cancer? The epidemiological evidence of the association is bulletproof. However, the majority of smokers don’t get lung cancer. In fact, there are complex statistical models that allow a pretty accurate calculation of risk in populations based on how long and how much a smoker has been smoking. For example, if you start smoking at age 18 and smoke two packs a day, by age 55, you have about a 5% chance of dying of lung cancer and by age 75 you have about a 20% chance of dying of lung cancer. That’s a far lower chance than an HIV-positive patient has of progressing to full-blown AIDS in 10 years (approximately 50%); yet no one seriously disputes that smoking is a very strong risk factor for lung cancer. At the population level, the association is very strong. However, if I see a 65-year-old patient who has been smoking since age 18, I can’t tell him whether he will definitely get lung cancer. I can only quote probabilities. Between two 65-year-olds who are heavy smokers, one may be perfectly fine and another may have stage IV lung cancer.

Let’s look at another example: Breast cancer. Let’s look at stage IV disease, which is, in essence, 100% fatal eventually. However, we do have pretty good estimates of median survival and what a patient’s chance of living 6, 12, 24, and 36 months are. However, when faced with a single breast cancer patient with stage IV disease, we are pretty poor at predicting how long that particular patient will survive. We can’t give a good answer to this poor hypothetical patient’s question, “How long have I got left?” We can only quote probabilities. One woman might deteriorate and die in 6 months, while all of us involved in the care of breast cancer patients have seen the occasional patient who has lived with metastatic disease for several years and done mostly well.

Examples like this abound in the medical literature. The fact that HIV “dissidents” again think this new paper describes some phenomenon unique to HIV again shows their ignorance of the totality of the biomedical literature.

HIV/AIDS and viral load

Ah, another day, another paper for the anti-HIV establishment to glom onto and misrepresent.

Last week’s issue of the Journal of the American Medical Association published this paper examining the relationship between HIV load and CD4 T-cell decline:

Context Plasma human immunodeficiency virus (HIV) RNA level predicts HIV disease progression, but the extent to which it explains the variability in rate of CD4 cell depletion is poorly characterized.

Main Outcome Measures The extent to which presenting plasma HIV RNA level could explain the rate of model-derived yearly CD4 cell loss, as estimated by the coefficient of determination (R2).

Results In both cohorts, higher presenting HIV RNA levels were associated with greater subsequent CD4 cell decline. In the study cohort, median model-estimated CD4 cell decrease among participants with HIV RNA levels of 500 or less, 501 to 2000, 2001 to 10 000, 10 001 to 40 000, and more than 40 000 copies/mL were 20, 39, 48, 56, and 78 cells/µL, respectively. Despite this trend across broad categories of HIV RNA levels, only a small proportion of CD4 cell loss variability (4%-6%) could be explained by presenting plasma HIV RNA level. Analyses using multiple HIV RNA measurements or restricting to participants with high HIV RNA levels improved this correlation minimally (R2, 0.09), and measurement error was estimated to attenuate these associations only marginally (deattenuated R2 in the 2 cohorts, 0.05 and 0.08, respectively).

Conclusions Presenting HIV RNA level predicts the rate of CD4 cell decline only minimally in untreated persons. Other factors, as yet undefined, likely drive CD4 cell losses in HIV infection. These findings have implications for treatment decisions in HIV infection and for understanding the pathogenesis of progressive immune deficiency.

The deniers, of course, have taken that last portion, twisted it, and used it like they used the Padian paper: to somehow suggest that the HIV–>AIDS paradigm isn’t true, and experts are just “bunglers.” More on what the actual research shows–and what the study authors say about their paper–below.
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