When Does CD4 Cell Count Plateau? Evidence from Patients Treated with Lopinavir/ritonavir for up to 7 Years It is unclear how long subjects who receive long-term antiretroviral therapy can maintain continued CD4 cell count increases. Previous studies have generally suggested a plateau 3-4 years after treatment initiation. Researchers from Abbott Laboratories analyzed CD4 cell count changes from baseline in 100 antiretroviral-naive subjects treated with lopinavir/ritonavir (Kaletra) + d4T (stavudine; Zerit) + 3TC (lamivudine; Epivir) for up to 7 years (360 weeks). Results were presented at the 46th Interscience Conference on Antimicrobial Agents and Chemotherapy taking place this week in San Francisco. The investigators used nonlinear regression to fit a segmented model (by baseline CD4 cell count strata) consisting of a quadratic model followed by a plateau. Results
Conclusion "Based on a model that explicitly identifies a time of CD4 plateau," the researchers concluded, "antiretroviral-naive subjects treated with lopinavir/ritonavir-based regimens with lower baseline CD4 counts had longer durations of CD4 increases (up to 7 years for subjects with baseline CD4 below 50 cells/mm3), but CD4 values did not catch up to those who started with higher CD4 counts at baseline." They added that, "Results compare favorably to [those of] previous studies that have suggested CD4 plateaus at earlier timepoints, lower final CD4 counts, or both." Abbott Laboratories, Abbott Park, IL. 09/29/06 Reference
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Mean baseline CD4 cell counts were 485, 129, and 24 cells/mm3, respectively, for
subjects with baseline CD4 counts greater than 200 cells/mm3 (n = 64), 50-199
cells/mm3 (n = 19), and below 50 cells/mm3 (n = 17). 
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