Integrated Regional Information Networks - November 4, 2003

A study conducted by researchers in Zambia's University Teaching Hospital and the University College in London, has found that spots of dried blood, filter paper and inexpensive commercially available chemicals, could be developed into a "field-friendly alternative" to the sophisticated technology required to carry out CD4 count testing. A CD4 count measures the strength of the immune system.

Existing guidelines for managing patients on antiretroviral (ARV) therapy use viral load and CD4 count testing to measure the impact of ARVs on the patient's health.

Although ARVs are increasingly becoming available in African countries at reduced prices, the high cost of monitoring equipment remains one of the biggest obstacles.

In Zambia, where the government has announced plans to treat up to 10,000 HIV-positive people in state hospitals and clinics, a CD4 count test can cost up to US $40.

"But the equipment for measuring CD4 counts is not widely available and is limited to tertiary institutions and private hospitals," Dr Peter Mwaba of the University Teaching Hospital, and one of the study's researchers, told IRIN.

According to the study findings published in the UK-based Lancet Journal, "the present gold standard" for CD4 count tests was the flow cytometer - a machine which counts cells as they go through a laser beam.

"There are a lot of tests that are used to measure CD4 count and viral load. But with all these tests, fresh samples of blood are required. This is not practical in countries like mine where there are no laboratory facilities in rural areas," Mwaba commented.

Researchers at the University Teaching Hospital took blood spots from 42 HIV-positive patients and put them on filter paper, which was allowed to dry.

The test samples were then sent to a central clinic without refrigeration.

The blood spots were analysed using a simple test involving antibodies that latched onto CD4 cells. The bound antibodies caused a colour change in a solution made from the dried blood: a deeper colour equaled a higher cell count.

The report found that filter papers offered "an attractive alternative to use of fresh whole blood. Once the samples have dried, the filter papers can be stored at room temperatures for long periods before being batched and sent to a central laboratory."

"The results compared very well to the [flow] cytometer - there were some very slight variations but these won't change the meaning of the result," Mwaba noted.

He pointed out, however, that the new technique still needed to be refined. "We can't get excited on 42 patients, we are planning on expanding the tests and we are looking at a larger trials involving about 1,000 patients."

Nevertheless, the implications for African countries considering the roll-out of ARVs can not be ignored. A CD4 count using this new method could cost up to US $5 in the developing world and patients receiving treatment could also be managed properly, he said.

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