Biomedical Engineering Reference
In-Depth Information
this FACSCount system provides for the testing of CD4 percentage as well as CD4
absolute values. The Guava EZCD4 system measures the absolute CD4 values
directly by using a microcapillary fixed volume method. In the Guava system,
separate two-color panels of CD3/CD4 and CD3/CD8 are available for testing.
Becton Dickinson FACSCount and Guava EZCD4 systems are FDA approved. In
addition to the dedicated CD4 flow cytometry systems, there are single and dual
platform methods available to perform CD4 absolute counts. Among the manufac-
turers of these flow cytometry systems are Accuri Cytometers (Accuri Cytometers
Inc., Ann Arbor, MI), Beckman Coulter, Becton Dickinson, Partec (Partec GmbH,
Muester, Germany), and PointCare (PointCare Technologies, Marlborough, MA). A
flow cytometric method called Pan-Leukogate or PLG CD4 was recently introduced
by investigators at the National Health Laboratory Systems in the Republic of South
Africa. This counting approach uses a two-color antibody panel to report percentage
and absolute CD4 values. The reagent used in this method is licensed through
Beckman Coulter (Beckman Coulter, Inc., Miami, FL) and is compatible with most
cytometry systems. Several new nonflow cytometric systems are in development to
perform CD4 testing. LabNow (LabNow, Inc., Austin, TX) and Zyomyx (Zyomyx,
Inc., Hayward, CA) use microchip-based technology to test for both percent and
absolute values. Point-of-care technology developed by Beckman Coulter, Burnet
Institute, and Millennium Biotechnology use a rapid low-technology dipstick-like
approach for semiquantitative evaluation of CD4 values.
8.6 FUTURE OF CD4 T CELL ASSESSMENT METHODOLOGIES AND
TECHNOLOGIES
Strategies to develop low-cost laboratory assays with high degree of accuracy and
precision are more pronounced in the management and treatment of HIV than with
any other disease. This is particularly relevant to sustaining the level of care of this
disease in countries with limited resources. The challenge is to deliver a system of
testing that is accurate, simple, low cost, and readily available in local settings.
Initiatives supported by private industry as well as government and private funding are
underway to develop such a system. There are several fronts emerging from these
initiatives. In the area of instrumentation, the development of a compact and simple
flow cytometer is the focus of manufacturers, old and new alike. In the area of reagent
development, the reintroduction of lyophilization technology is advancing the field in
reducing the cost related to reagent transport and storage. The removal of refrigeration
needs in the handling of these lyophilized reagents is a considerable cost savings
factor. In the area of system innovations, the development of a point-of-care method
for CD4 testing is gaining the most fervor. The point-of-care system will provide
accurate and reliable testing in remote as well as well-populated areas where decisions
to start drug treatment depend on quick and easily obtained CD4 counts.
CD4 T cell assessments are useful prognostic markers in HIV infection because
they can indicate disease progression and drug adherence or resistance and suscept-
ibility to OIs. They are invaluable for use in clinical trials to assess the efficacy and
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