Andrew Phillips and his European colleagues have analyzed the viral load response in the largest group of antiretroviral naïve people beginning at least a three-drug antiretroviral regimen (ART). The study, "HIV Viral Load Response to Antiretroviral Therapy According to the Baseline CD4 Cell Count and Viral Load," is reported in the November 28, 2001, issue of JAMA. The study combined three large European cohorts (groups of people), the Swiss HIV Cohort Study, the Frankfurt HIV Clinic Cohort, and the EuroSIDA Study Group, for a total of 3,226 people. Unlike some other studies that included people who had prior therapy with one or two drugs, the people in this study had no prior therapy for HIV before beginning at least a three-drug combination after January 1, 1996. The purpose of this study was to "characterize the relationship of viral load response to ART with baseline CD4 count and baseline viral load."

People were analyzed according to baseline CD4 cell count (below 200, 200 to 349, and 350 or more), and baseline viral load (below 10,000, 10,000 to 99,999, 100,000 or more). The authors analyzed the number of people who achieved a viral load below 500 after initiating therapy, and the number who had viral rebound to more than 500. There were no significant differences observed in the number of people achieving a viral load below 500, or in the number who had viral rebound based on the starting CD4 cell count or viral load. There were no differences observed based on gender. The only difference noted was that in the high viral load group, 100,000 or more, it took longer to achieve viral suppression. Overall, 85% of people achieved viral suppression. The death rate was higher in the people who started ART with a CD4 cell count below 200, but was not different in the other two groups, 200 to 349, and 350 or more.

The authors note that a retrospective cohort study such as this cannot definitively answer the question of when to start ART, but the data does help provide some guidance to clinicians and people with HIV. Also, they note that the low clinical events rate observed in this study "indicate[s] that a randomized trial of immediate vs. deferred therapy would likely have to be very large and last several years." This study does provide some data which questions the prevailing wisdom that it is easier to achieve durable virologic suppression if you begin ART at a higher CD4 cell count, or lower viral load.