One of the biggest obstacles hampering the campaign to distribute anti-HIV drugs across Africa may have been overcome by a technique that is simple, rugged and cheap, a study says.
Using just ordinary filter paper and inexpensive commercially-available reagents, researchers report they were able to replicate tests normally carried out by sophisticated machines to evaluate a patient's immune health.
"The results are wonderful. They help the search for something that is inexpensive, reliable and effective," lead author Alimuddin Zumla, a professor at the Centre for Infectious Diseases and International Health at University College London, told AFP.
Carrying out a count of so-called CD4 immune cells is vital for figuring out whether an individual is responding to anti-retroviral drugs.
In rich countries, CD4 counts are carried out by a flow cytometer, a machine which counts cells as they pass through a laser beam.
These gadgets are expensive to buy -- around $US35,000 ($A49,846) each -- and need to be staffed and maintained by trained technicians. Blood samples have to be fresh, which in practical terms means that the patient has to be within a travelling distance of two hours from the lab.
All that represents a crippling burden for poor, under-equipped African countries that are bearing the brunt of the global HIV/AIDS epidemic.
Writing in next Saturday's issue of The Lancet, Zumla's team took blood from 42 HIV-infected volunteers in Zambia.
The blood was allowed to dry on filter paper and was then sent off to a laboratory, which used chemicals known as buffers to leach out the blood.
The blood was then put through a CD4 count using a far cheaper, although less precise, antibody technique called the ELISA process.
The same blood samples, carefully refrigerated and rushed to a specialist lab, were also tested by a flow cytometer, the "gold standard" for accuracy.
The rule of thumb with CD4 counts is that people with less than 200 cells per microlitre of blood have a damaged immune system and are a candidate for antiretrovirals.
These are the triple "cocktail" of HIV-suppressing drugs that have revolutionised life for patients in rich Western countries.
They are now progressively entering poorer countries, thanks to swinging price cuts by pharmaceutical companies and the prospect of competition by "generic" copies of patented drugs.
The filter paper/ELISA method scored well in comparison with the flow cytometer. It was not as precise -- the variation was on average about 20 per cent -- but that difference narrowed when a patient was above the important 200 count.
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