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Monitoring Plasma HIV-1 RNA Levels in Addition to CD4+ Lymphocyte Count Improves Assessment of Antiretroviral Therapeutic Response

Michael D. Hughes, PhD; Victoria A. Johnson, MD; Martin S. Hirsch, MD; James W. Bremer, PhD; Tarek Elbeik, PhD; Alejo Erice, MD; Daniel R. Kuritzkes, MD; Walter A. Scott, PhD; Stephen A. Spector, MD; Nesli Basgoz, MD; Margaret A. Fischl, MD; and Richard T. D'Aquila, MD,
[+] Article and Author Information

for the ACTG 241 Protocol Virology Substudy Team. For author affiliations and current author addresses, see end of text. *For additional members of the ACTG 241 Protocol Virology Substudy Team and participating centers and virology laboratories, see the Appendix. Note: Supplemental support for some virology studies was provided by Boehringer Ingelheim Pharmaceuticals, Inc. Study medications were provided by Boehringer Ingelheim Pharmaceuticals, Inc.; Bristol-Myers Squibb Company; and Glaxo Wellcome Company. Acknowledgments: The authors thank the patients and staff who contributed to the study. Grant Support: In part by the AIDS Clinical Trials Group and grants AI-27661, AI-27675, AI-29193, AI-32770, AI-32775, and AI-32794 from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health. Requests for Reprints: Michael D. Hughes, PhD, Medical Statistics Unit, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, England, United Kingdom. Current Author Addresses: Dr. Hughes: Medical Statistics Unit, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, England, United Kingdom.


Copyright ©2004 by the American College of Physicians


Ann Intern Med. 1997;126(12):929-938. doi:10.7326/0003-4819-126-12-199706150-00001
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Background: CD4+ lymphocyte counts and plasma HIV-1 RNA levels predict progression of HIV-related disease, but the relative importance of these and other virological factors in defining response to antiretroviral therapy is not yet clear.

Objective: To determine the short-term variability of plasma HIV-1 RNA level during stable therapy; the relative importance of pretreatment values and early changes in CD4+ count, HIV-1 RNA levels, and infectious HIV-1 titers in mononuclear cells of peripheral blood and pretreatment syncytium-inducing phenotype of an HIV-1 isolate for prediction of disease progression and decline in CD4+ counts during therapy.

Design: Data were collected prospectively in a randomized, clinical trial comparing two combination regimens (ACTG [AIDS Clinical Trials Group] Protocol 241) and pooled across treatments.

Setting: 8 AIDS Clinical Trials Units.

Patients: 198 adults with HIV-1 infection and no more than 350 CD4+ lymphocytes/mm3 who had received at least 6 months of nucleoside therapy.

Interventions: All patients received zidovudine and didanosine; 100 received nevirapine and 98 received placebo.

Measurements: CD4+ lymphocyte counts, plasma HIV-1 RNA levels, and infectious HIV-1 titers in cells were measured before and 8 and 48 weeks after study treatment. Assay for the syncytium-inducing viral phenotype was done at baseline. Progression was defined as occurrence of opportunistic infection, malignancy, or death during the 48 weeks after treatment began.

Results: The difference between two measurements of HIV-1 RNA levels at baseline was within ± 0.39 log10 copies/mL (2.5-fold) for 90% of 167 patients receiving stable therapy. In a multivariate model, risk for disease progression was reduced by 56% (95% CI, 8% to 79% [P = 0.028]) for every 10-fold lower HIV-1 RNA level at baseline, by 52% (CI, 6% increase to 79% reduction [P = 0.071]) for every 10-fold reduction in HIV-1 RNA level at 8 weeks after treatment initiation, and by 67% (CI, 42% to 81% [P < 0.001]) for every 2-fold higher CD4+ count at baseline. These risk factors and syncytium-inducing viral phenotype at baseline, but not infectious HIV-1 titers in circulating cells, were associated with change in CD4+ counts over 48 weeks.

Conclusions: For an individual patient, a change in plasma HIV-1 RNA level of 2.5-fold or more probably indicates a true biological change. Monitoring HIV-1 RNA levels and CD4+ lymphocytes before a change in antiretroviral treatment and monitoring HIV-1 RNA levels shortly thereafter improves prediction of disease progression and decline in CD4+ counts for 1 year compared with monitoring CD4+ counts or HIV-1 RNA levels alone. Additional monitoring of infectious HIV-1 titers in mononuclear cells of peripheral blood is not useful.

Figures

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Figure 1.
Differences between entry and preentry measurements of plasma human immunodeficiency virus type 1 (HIV-1) RNA level compared with the mean of the two measurements (the baseline level).

The dashed lines represent the 5th and 95th percentiles for the differences while patients were receiving stable treatment and before study treatment was initiated. Five patients had both the preentry and entry plasma HIV-1 RNA levels below the detectable limit, and one patient had one of the two measurements below the limit.

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Figure 2.
Association between measurements of plasma human immunodeficiency virus type 1 (HIV-1) RNA level and CD4+ lymphocyte count at study entry.

The dashed lines represent 95% Cls.

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Figure 3.
Association between long-term change from baseline to week 48 in CD4+ lymphocyte count.Top.Bottom.

Plotted against baseline plasma human immunodeficiency virus type 1 (HIV-1) RNA level. Plotted against the early change from baseline to week 8 in plasma HIV-1 RNA level. The dashed lines represent 95% Cls.

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