The study's lead author, Bryan Lau, a graduate student in the School's Department of Epidemiology, said, "This study demonstrates that there is a biological event that occurs during the progression of HIV infection leading to declines in TLC and Hgb within individuals. The majority of HIV individuals who develop AIDS experience a rapid decline in total lymphocyte counts and hemoglobin concentration that starts about one and one-half years prior to developing AIDS. The decline in these two markers in individuals who develop AIDS shows that this is an important event in the pathogenesis of the disease."
The study authors analyzed longitudinal measurements of TLC and Hgb in 3,299 homosexual and bisexual men enrolled in the Multicenter AIDS Cohort Study (MACS) from 1984-1991. The researchers found that for many years after HIV infection, TLC and Hgb markers are stable and provide little information about HIV disease progression to AIDS.
However, as HIV disease progresses, TLC and Hgb begin to decline rapidly. A TLC decline greater than 10 percent per year and Hgb decline greater than 2.2 percent per year was present in over 77 percent of the study participants who developed AIDS and absent from over 78 percent of individuals who did not develop AIDS.
To further support their findings, the researchers explain in their study that current World Health Organization guidelines suggest the use of TLC measurements for monitoring an individual's HIV infection in developing countries if CD4+ cell counts are not known. Hgb levels have also been shown to have an association with progression from asymptomatic HIV infection to AIDS.
Currently, in order to begin antiretroviral therapy for asymptomatic HIV-infected individuals, measurements of HIV RNA levels and CD4+ lymphocyte counts in the blood are required. These measurements are expensive and require technological expertise and equipment that is typically not available in developing countries.
Joseph Margolick, a contributing author and professor in the School's Department of Molecular Microbiology and Immunology, said, "These results could be very useful for regions with scarce heath-care resources as an alternative way of identifying individuals who should receive drug therapy for HIV infection. We believe further research in appropriate populations is warranted."
Stephen J. Gange, Adjunct Associate Professor in the School's Department of Epidemiology, and Joseph B. Margolick, Professor in the Department of Molecular Microbiology and Immunology, co-authored the study. Additional co-authors are John P. Phair, with Northwestern University Medical School, Sharon A. Riddler, with the University of Pittsburgh, and Roger Detels, with UCLA's School of Public Health.
The MACS is funded by the National Institute of Allergy and Infectious Diseases and the National Cancer Institute.
Link to the Johns Hopkins Bloomberg School of Public Health at http://www.jhsph.edu.
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