Cheap test monitors HIV drugs

HELEN PEARSON

Fresh blood tests to monitor HIV progress cost around $40 each time. © alamy.com

Spots of dried blood could help to monitor the success of HIV drugs in the developing world, say disease researchers. A cheap test is vital now that anti-AIDS medications are increasingly available to poor nations, thanks to charitable subsidies and cheaper, generic versions.

Antiretroviral drugs stop the AIDS virus from killing key immune cells in the blood. But patients in Africa, for example, often miss out on essential blood-cell monitoring because it requires fresh, refrigerated blood and expensive analytical machines.

Instead, "You just need a finger prick", says Alimuddin Zumla of University College London. In a trial on 42 Zambian patients, Zumla's team has shown that cell counts obtained using dried blood spots are largely comparable to those from hi-tech monitoring¹.

Using dried blood "would be fantastic", says HIV researcher Susan Fiscus of the University of North Carolina at Chapel Hill. Monitoring blood for cell counts or viral levels is essential to check that patients are taking their medicines, or to ensure that the virus has not become resistant to the drugs given - if so, the drug cocktail must be adjusted, she explains.

In Western clinics, doctors probe fresh blood samples by mixing them with fluorescent antibodies that latch onto critical immune cells called CD4+ lymphocytes. The fluorescent cells are sorted and counted in a machine. The procedure costs up to $40 a go.

In Zumla's test, blood spots on filter paper are allowed to dry, then ferried to a central clinic without refrigeration. This is vital in developing countries, where many rural patients live far from urban clinics.

Technicians analyse the blood spots using a simple, commercially available test involving antibodies that latch onto CD4+ lymphocytes. The bound antibodies cause a colour change in a solution made from the dried blood: a deeper colour equals a higher cell count.

Zumla says that he has already adapted the prototype so that it can also gauge levels of the AIDS virus, another key indicator of treatment success. It costs around $1 per test, he says. Cheaper reagents could slash it to only 20 cents.

The team now hopes to perfect the test in collaboration with HIV clinics in several countries, including Zambia, Malawi, Tanzania, South Africa, Ethiopia, Gambia and Madagascar. They are also looking for a company to develop it.

1. Mwaba, P. et al. Use of dried whole blood spots to measure CD4+ lymphocyte counts in HIV-1-infected patients. Lancet, 362, 1459 - 1460, (2003). |Homepage|