More than 30 million people in developing countries are living with HIV infection with almost 3 million new infections each year. The global burden of this disease is not equitable. For instance, in North America the incidence rate is 0.5% while in Africa it is 4.7%, with some countries having incidence rates of over 20% (WHO). Of the 33 million people living with HIV/AIDS, 22 million of them reside in sub-Saharan Africa; making low cost, portable care a necessity. An enormous global effort is now underway to bring antiretroviral treatment to those in low to middle income countries; resulting in a recent 17% decrease in incidence(WHO). Moreover, 20% less people died in sub-Saharan Africa in 2009 versus 2004, largely due to this effort. 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.
Methods and Findings
We have developed 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 miniaturized flow cell and imaged through a fluorescent misroscope with attached CCD. An associated computer algorithm, utilizing ImageJ (NIH) 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.
Relevant Papers
Rodriguez et al., “A Microchip CD4 Counting Method for HIV Monitoring in Resource-Poor Settings”, PLoS Medicine, 2005.
Jokerst et al., “Integration of semiconductor quantum dots into nano-bio-chip systems for enumeration of CD4+ T cell counts at the point-of-need”, Lab on a Chip, 2008.