Practical HIV diagnostics are urgently needed in resource-limited settings. While HIV infection can be diagnosed using simple, rapid, lateral flow immunoassays, HIV disease staging and treatment monitoring require accurate counting of a particular white blood cell subset, the CD4(+) T lymphocyte.
Current systems for providing this function are expensive, technically demanding and/or time-consuming. For example, CD4 counts may be obtained by conventional flow cytometry. The method requires a slow flow rate to capture the cells on the surface of the channel, followed by a quick wash. This is not easy to implement in a point-of-care device, where the fluid actuation technique must be fairly simple. They require a microscope and a camera (or a person) to count the captured cells. This method is suitable for a lab environment, not point of care.