December 18, 2001
While the majority of people starting antiretroviral therapy experience a significant CD4 cell count increase -- greater than 100 cells -- some have relatively small increases, even when their viral load is undetectable. This poster by Dr. Dronda from Madrid attempted to find predictors of this suboptimal response.
The study was an observational cohort of 503 patients who started antiretroviral therapy after March 1996. Included in this analysis were only the 288 patients who achieved virologic suppression, here defined as an HIV RNA <50 copies/mL. The mean age of this group was 36, with 74 percent men.
Out of this group, at 12 months, 76 of 288 (26 percent) did not experience a CD4 cell count increase of at least 100 cells; after 24 months, 42 (16 percent) still had not reached this threshold. The investigators looked at potential risk factors for this poor CD4 cell response, including several that have been reported previously, such as age, gender, mode of HIV acquisition, baseline viral load, baseline CD4, protease inhibitor versus non-protease-inhibitor containing regimen, history of AIDS, hepatitis C co-infection, and whether the regimen included AZT or d4T. By multivariate analysis, only two of these factors independently predicted a suboptimal response -- a history of intravenous drug use, and treatment with a non-protease-inhibitor-containing regimen.
It should be emphasized that clinical events in this group were infrequent, and not surprisingly limited to those with low baseline CD4 counts. Therefore, one could argue that the clinical relevance is mainly for this severely immunosuppressed group, since it probably does not matter whether a baseline CD4 cell count increases from 300 to 350 or 500 -- the risk of developing an opportunistic infection would be extremely low for both values, especially while receiving suppressive antiretroviral therapy. The observation of the different effects of protease inhibitor versus non-protease-inhibitor-containing regimens has not been consistently reported, and needs to be investigated further.
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