AIDSWEEKLY Plus; Monday, October 24, 2005
Staff Medical Writers

"Our objective was to develop data-based algorithms for definition of immunologic response to AIDS therapies in pediatric patients, taking account of T-cell subset measurement errors. The study design involved cross-protocol analysis of 2,148 enrollees in 6 completed Pediatric AIDS Clinical Trials Group trials," researchers in the United States report.

"We used standard quantitation of T-cell subsets; linear modeling with mean-dependent measurement error variance was used to develop 95% tolerance limits for change in CD4%.

"For individuals with a CD4% of approximately 25%, the measurement error-based 95% tolerance interval ranges from 15 to 35%, whereas for individuals with a CD4% of approximately 5%, the tolerance interval ranges from 3 to 7%," said the authors.

"When pairs of CD4% measures taken within a time interval of less than 30 days are averaged to estimate steady-state CD4%, tolerance interval width decreases by approximately 30%.

"A simple graphical tool that provides a data-based criterion for immunologic response over and above variation ascribable to T-cell measurement error is provided," wrote V.J. Carey and colleagues at Harvard University.

Scientists concluded, "Variability in CD4% due to measurement error is substantial, increases with level of CD4%, and complicates assessment of immunologic response to therapy. Replicates of CD4% measures could be used to improve precision of interpretation of CD4% measures."

Carey and colleagues published their study in Clinical and Diagnostic Laboratory Immunology (Reliability of CD4 quantitation in human immunodeficiency virus-positive children: Implications for definition of immunologic response to highly active antiretroviral therapy. Clin Diagn Lab Immunol. 2005 May;12(5):640-3.

For additional information, contact V.J. Carey, Harvard University, Brigham & Women's Hospital, Channing Laboratory, School Publ Health, Center Biostatistics AIDS Research, 181 Longwood Avenue, Boston, MA 02115, USA.

Publisher contact information for the journal Clinical and Diagnostic Laboratory Immunology is: American Society Microbiology, 1752 N St. NW, Washington, DC 20036-2904, USA.

Keywords: Boston, Massachusetts, United States, HIV/AIDS, Diagnostics, Pediatrics, CD4% , Measurement Error.

This article was prepared by AIDS Weekly editors from staff and other reports.

Reference

Carey VJ, Pahwa S, Weinberg A. Reliability of CD4 quantitation in human immunodeficiency virus-positive children: implications for definition of immunologic response to highly active antiretroviral therapy, Clin Diagn Lab Immunol. 2005 May;12(5):640-3.

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