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Researchers have developed a cheap, fast and portable way of monitoring HIV patients' immune systems.

They aim to develop it into a handheld device that could greatly improve HIV treatment for people living in rural areas in poor countries with few medical resources.

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 in developed countries 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 had no access to proper treatment.

In a paper published by PLoS Medicine this month, researchers say that initial tests in 61 adults and six children showed that their device is just as effective as the existing method.

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 research team, led by John T. McDevitt, University of Texas, United States, says that because the device needs only tiny amounts of blood, healthcare workers using it would be less exposed to HIV infection.

The need to develop the prototype is urgent, says Zvi Bentwich, professor of medicine at Hebrew University Medical School, in an accompanying article in the journal.

Bentwich comments that most efforts to provide antiretroviral drugs to people with HIV in developing countries would be "highly likely to fail" unless there is a better way of identifying those who need treatment.

Gabi Vercauteren, at the World Health Organization's department of essential health technologies, told SciDev.Net that the device could bring CD4 monitoring to people who currently have little access to it.

But she warns that introducing a portable technology would mean that each healthcare worker would hold their own set of data, whereas in a centralised laboratory information on people's HIV status would be kept in one place.

Collating this data is important for long-term monitoring of HIV both locally and nationally.

Vercauteren also raised the question of how much the device would cost, something the researchers did not specify in their paper, nor in interviews with SciDev.Net.

A company called LabNow is developing the technology further, says William Rodriguez, lead author of the PLoS Medicine paper, who is based at the Partners AIDS Research Center, Massachusetts General Hospital, United States.

Rodriguez and colleagues are now working on "even simpler miniaturisation technologies to develop an even faster and less expensive CD4 device".

Link to paper by William Rodriguez and colleagues

Link to paper by Zvi Bentwich

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