March 1, 2011
The following is our transcript of a press conference that took place on Feb. 28, the first full day of CROI 2011. In it, Heather Ribuado, Ph.D., summarized the findings of a study she was presenting at the conference entitled, "Race Differences in the Efficacy of Initial ART on HIV Infection in Randomized Trials Undertaken by ACTG." The chief finding from her study was that African Americans were 40% more likely (after adjusting for confounding factors) to experience virologic failure on any antiretroviral regimen.
Heather Ribaudo: I'm reporting on an individual patient meta-analysis of five ACTG clinical trials, in which we were looking at virologic outcomes in just a little under 2,500 non-Hispanic white and non-Hispanic black individuals. The study spans a period of about seven years.
We found that black race was associated with about a 60% increase in the rate of virologic failure. We found this effect was very consistent across all the different treatment regimens that patients were taking throughout the course of the different studies. And we also found that even after we adjusted for potential confounding factors, the effect persisted -- was a little bit attenuated [to 40%], but we still found an increase in the risk of virologic failure in black individuals compared to white individuals.
Our association was very robust in analyses that attempted [to account] for differential rates of treatment discontinuation among the population. We did an as-treated analysis and an analysis that looked at discontinuation of treatment also as an end point in our study. Our result was very consistently seen; we still found this significant increase in failure.
On the upside, we did find that black race was associated with a quite modestly higher increase in CD4-cell counts over a 96-week period. That effect is very modest, around a 30-cell increase in an adjusted analysis. So it's unclear whether that really has any clinical relevance.
I do want to note a few limitations to the analysis, in that the adherence measure we used to adjust in our analysis was very broad. It was based on four-day recall, and really just looked at whether the patients had missed any doses over that four-day recall. So we weren't able to adjust for different patterns of adherence that might have existed in the population.
I think, as well, we only measured the social factors -- that I think are very important in this area -- we were only able to measure those on a subset of our population. We weren't able to capture some, I think, key social factors that might be a measure of more challenging life situations that patients might face, such as housing status, income level and the number of dependents in a family.
Reporter #1: Have you looked at all whether there was some kind of genetic difference here, like the IL-28 in HCV (hepatitis C virus), which would differentiate response?
Heather Ribaudo: We have not at this point looked at genetics. It is an interesting idea. Actually, we have a poster that we're presenting here -- poster 477, I believe it is -- that one of my colleagues is presenting. We did look at virologic outcome in a subset of these patients, actually. We did not in a GWA [genome-wide association] study and we did not find any genetic associations in that study. In this exact cohort we have not.
Reporter #2: A possible explanation for this phenomenon? And was it the first time that this was reported?
Heather Ribaudo: It has been seen in other studies over the last five years or so. A couple of studies that did well adjust for access to health care, those studies did not find such an association. I really wish we'd been able to better capture some of these social factors. Those social factors, to me, may be some of the key issues that might help explain this -- those people with very challenging life situations.
Reporter #3: This is a comment, really, more than a question, because I suspect it is social factors. Because in the UK [United Kingdom], where we have a fairly open-access health system, there is no difference in treatment outcomes between two white, UK, gay men and sub-Saharan Africans, who are basically the two main populations in the epidemic in the country. You'd expect to see the same difference if it were genetic.
Heather Ribaudo: I think, with the genetic association: The fact that we saw this [racial disparity in virologic failure] very consistently across a broad range of regimens -- in terms of a pharmacogenetic association, anyway, I think it's less likely to be associated.
This transcript has been lightly edited for clarity.
No comments have been made.
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