Abstract
Background: More than 25 million people in developing countries are living with HIV infection. An enormous global effort is now underway to bring antiretroviral treatment to at least 2.5 million of those infected. While drug prices have dropped considerably, the cost and technical complexity of laboratory tests essential for the management of HIV disease, such as CD4 cell counts, remain prohibitive. New, simple, and affordable methods for measuring CD4 cells that can be implemented in resource-scarce settings are urgently needed [5, 6]. Methods and Findings: Here we describe the development of a prototype for a simple, rapid, and affordable method for counting CD4 lymphocytes. Microliter volumes of blood without further sample preparation are stained with fluorescent antibodies, captured on a membrane within a minimized flow cell and imaged through microscope optics with the type of charge-coupled device developed for digital camera technology [10]. An associated computer algorithm converts the raw digital image into absolute CD4 counts and CD4 percentages in real time. The accuracy of this prototype system was validated through testing in the United States and Botswana, and showed close agreement with standard flow cytometry (r = 0.95) over a range of absolute CD4 counts, and the ability to discriminate clinically relevant CD4 count thresholds with high sensitivity and specificity [1,4]
Highlights
More than 25 million HIV-infected people live in developing countries with significant resource limitations
In initial experiments using the original electronic taste chip (ETC) system [21,22,23], microspheres were coated with monoclonal antibodies to the lymphocyte surface markers CD3, CD4, or CD8, followed by microfluidic delivery of fluorescently labeled lymphocytes from whole blood obtained from non-HIV-infected participants
Lymphocytes were readily captured, precise quantification of cell numbers and CD4 cell counts were not possible using the microsphere as a surface for lymphocyte capture
Summary
More than 25 million HIV-infected people live in developing countries with significant resource limitations. 5 million people living in developing countries are in urgent need of antiretroviral therapy, only 600,000 to 700,000 currently receive effective treatment [1, 2]. While the cost of antiretroviral medications has dropped considerably, other obstacles, including the cost, technical, and operational requirements of CD4 counts, viral loads, and other sophisticated diagnostic tests used to initiate and monitor HIV treatment, remain to be addressed [5]. Doctors know whether or not a patient's immune system is healthy-and whether or not to start treatment-by measuring the "CD4 count." This is the number of CD4 cells in a sample of blood. CD4 counts should be determined before a patient receives antiretroviral therapy and measured regularly while the patient is on therapy
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