A handheld device could soon be aiding health workers in monitoring the immune system of HIV patients, reports science portal scidev.net.

Researchers led by John T. McDevitt, University of Texas, have found a way to monitor the immune systems of HIV patients, and now aim to develop it into a handheld device that could greatly improve treatment for people in the rural areas of poor countries.

To assess when to give HIV patients antiretroviral drugs, healthcare workers need to monitor the level of CD4 cells - a type of immune cell - in the patients' blood.

The current method of doing this is costly and requires large equipment and considerable technical expertise. As a result, many of the millions of HIV-infected people living in developing countries, often with inadequate healthcare, have no access to proper treatment.

Initial tests in 61 adults and six children showed that their device is just as effective as the existing method, the researchers said. The prototype works by mixing a drop of the patient's blood with antibodies - proteins produced by the immune system to fight infection - that bind only to CD4 cells.

The antibodies have been altered to fluoresce under certain conditions. This means that when a microscopic tool similar to a digital camera takes a picture of the blood sample, a microchip counts the number of CD4 cells automatically. The whole test takes about 10 minutes.

The researcher says that because the device needs only tiny amounts of blood, healthcare workers using it would be less exposed to HIV infection, the portal reported.