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Wednesday, July 25, 2007

Classic Dissident Viral Load Misunderstandings

I read a "quote" today from the good old denialists Andrew Maniotis

"...viral load is only able to predict progression to disease in 4% to 6% of HIV-positives studied, challenging much of the basis for current AIDS science and treatment policy" [Rodriquez B, Sethi AK, Cheruvu VK, et al. Predictive value of plasma HIV RNA level on rate of CD4 T-cell decline in untreated HIV infection. JAMA 296(12):1498-506, 2006;Cohen J. Study says HIV blood levels don't predict immune decline. Science 313(5795):1868, 2006. "

Of course this is related to the paper I referred to in an earlier post. As is typical for AIDS denialists, Maniotis is either unable to understand the science, or deliberately misrepresents it. He certainly "quotes" from the paper when in fact no such quote exists (it's one of his own!).

As Mellors and others have shown, viral load is actually predictive of progression to AIDS and death extremely well. In fact, in their original paper the researchers showed that this link was present regardless of baseline CD4 count. In full support of this, the Rodriguez article confirmed that in general viral load measurements were a good predictor of CD4 cell decline.

But, and listen closely, they said that absolute viral load only predicted 4-6% of the RATE of CD4 cell DECLINE. They didn't say that it only predicted it in 4-6% of patients, nor 4-6% of the CD4 cell count, and certainly didn't look at risk of AIDS or death.

In laymans' terms, if someone's CD4 cell count dropped by 100 over a year and someone else's CD4 count dropped by 200 over a year, only 4-6 of that difference of 100 could be statistically explained by having a higher viral load.

This is nothing new, as Rodriguez made clear - all the work did was quantitate the impact of one variable (viral load). Other factors would include the level of immune response, proviral load, nutritional status and even mental health (depression has been known to be linked to an increased risk of AIDS for years - similar to cancer).

No doubt this "4-6%" myth will propogate and mutate - which is why I'm posting. As I've said many times before - by all means criticize and debate, but don't do so from a position of pseudoscience.

4 Comments:

Blogger Martin PĂȘcheur said...

Dear Doctor

Thank you for the elucidation.

Are you saying viral load, in and of itself, is still the "powerful indicator" it has been touted as up till now, of disease progression and death?

Martin
letterstotheempire.blogspot.com

5:43 PM  
Blogger Jay said...

Dear Doctor

I have laid much store by your postings, but I have discovered you are being called an out-and-out liar here:

http://barnesworld.blogs.com/barnes_world/2006/10/by_jeffrey_dach.html

and here

http://barnesworld.blogs.com/Bennettsdeception.pdf

Please, Sir, for the sake of your honour, respond!

8:54 PM  
Blogger Bennett said...

Dear Jay (and CW, who's repost of an old Dach diatribe I rejected).

If I was worried about being called an out-and-out liar I'd have quit fighting the AIDS dissidents years ago.

I'm impressed that someone went to all the trouble of turning a perfectly good webpage into a PDF!

Being called a liar is not the same as being a liar. The facts bear that out. Whether someone else misunderstands or misrepresents the facts is up to them...I'm merely trying to educate.

Cheers

Bennett

9:51 PM  
Blogger Bennett said...

Martin - No-one other than the dissidents has put viral load up on a pedestal, and then only so they can knock it down.

The simple truth is that if you collect people with HIV together into groups, the group with the highest viral load does worse than the group with the lowest viral load, with the middle group in between. You cannot argue this point as it's simple observed truth. Those who do argue it are labeled as "denialists" for good reason...

The Rodriguez paper doesn't even look at disease progression or death, it looks at rate of CD4 count decline as a surrogate marker. Unsurprisingly, the individual variation on rate of CD4 count decline depends on more factors than the specific viral load value itself. Anyone who expects a simple, mathematical model to flow from biology doesn't understand biology!

Cheers

Bennett

9:58 PM  

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