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Another Lackluster Study on Predicting Response to HAART by CD4
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Brooks from the Centers for Disease Control and Prevention's Adult and Adolescent Spectrum of HIV Disease Working Project reported data on an attempt to evaluate the relationship of CD4 count before starting HAART and the response to HAART. First, keep in mind that patients were only followed for 12 months. Since follow-up is so short I'm not sure why this study was presented at this conference. This is a short time, after 3-5 years of following patients results might be different as more patients will fail HAART over more time. He found there was no difference in viral failure of HAART between patients with 200-349 CD4s or patients having >350 when they started HAART. In other words, patients who started HAART with 200-349 CD4s were no more likely to experience viral failure than patients who started HAART with CD4s >350, within the followup period of 12 months. Patients starting HAART with <200 CD4s had an increased risk for viral failure.
There are several qualifications for interpreting these study results. If you followed patients for a longer time of say 5 years, we could see patients with 200-349 CD4s experiencing more viral failure than patients with 350 or more CD4s when they started HAART. There have been numerous studies on this question. A number of them have suggested that when CD4s are 200-350 response to HAART is less than when CD4s are >350. This CDC study did not take into account the potency of the regimen and adherence factors. Patients with a lower CD4 count can respond better if they are given a potent regimen and if they are completely adherent. These considerations are not considered in this analysis and are often not considered in large studies of this type. I think both CD4 count and viral load before starting HAART can predict response.
This was a retrospective study of chart review and taking data from over 100
clinics around the United States controlling for demographics, opportunistic infections, year of highly active antiretroviral therapy (HAART) initiation,
and baseline viral load.
They evaluated only patients with a viral load response. Virologic failure (assuming an initial virologic response) was defined as either a >/= 0.5 log10 copies/mL increase in viral load from nadir, confirmed by a second test, or a switch in the regimen. Data sufficient for analysis were available from 583 patients who began HAART after 1996. Of these, 525 had an initial virologic response and were used for subsequent analysis. When stratified by baseline CD4+ cell count, virologic failure occurred in 18%, 16%, 7%, and 5% of those with 0-49, 50-199, 200-349, and > 350 cells, respectively. The patients in the lowest CD4+ cell count stratum failed 10.4 times faster than those in the highest stratum. There was no significant difference between those with 200-349 cells and those with > 350 cells. The estimated probability of failure at 6 months was 3.5% for the group with > 350 cells and 14% for the combined groups with < 200 cells. In a multivariable model, the CD4+ cell count was significantly associated with time to failure, but patient demographics, history of AIDS, antiretroviral regimen, clinical site, and baseline viral load were not.
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