Newer tests are cheap and easy to use.
You're in a small village in Mali. You have a fever, headaches and nausea, classic signs of malaria.
The most sensible thing would be for a technician at a clinic to prick your finger and examine the blood under a microscope. More likely, they'll simply assume you have malaria and hand you the medicines.
Most healthcare workers in remote African communities are ill-equipped, lacking the training or tools necessary to make sophisticated diagnoses. But indiscriminately treating all infections with malaria drugs is a sure way to exacerbate resistance to valuable drugs.
Confronted with this problem, scientists are scrambling to develop diagnostic tools that are practical and easy to use in even the most resource-poor settings.
In November, Johns Hopkins University scientists reported the first successful screening technique based on DNA from saliva or urine samples, rather than from blood. Researchers from the Geneva-based Foundation for Innovative New Diagnostics (FIND) have also devised a DNA-based test that, unlike other molecular tests, does not have to be sent away to a lab.
Bedside tests that can detect DNA and are quite cheap are the potential future. David Bell, World Health Organization
“Bedside tests that can detect DNA and are quite cheap are the potential future,” says David Bell, a malaria diagnostics expert at the World Health Organization.
Rapid tests—usually dipsticks that work like pregnancy tests—detect proteins that are produced by malaria parasites. The tests are simple and effective, and about 40 million of them were made in 2006. But their quality is inconsistent, and manufacturing flaws, such as differences in the quantity of reagents and components, affect their sensitivity (Nat. Rev. Microbiol. 4, 682–695; 2006).
The most accurate blood test detects the parasite's nucleic acids. But the technique is expensive and samples have to be sent to trained technicians in far-off labs.
FIND's new test, called loop-mediated isothermal amplification, or LAMP, is an inexpensive DNA test that any health worker with a heating source and basic lab skills and materials could use. The test will be ready for manufacturing in mid-2008, says Mark Perkins, chief scientific officer of FIND.
But highly sensitive assays such as LAMP can also detect parasites in people who are just carriers of the parasite and do not require treatment. In endemic regions there may be many of these individuals, and scientists will need to decide how best to use the tests there.
The saliva- and urine-based test, which must also be sent to labs, may prove more effective for research. In many countries where needles are taboo and AIDS is rampant, it can be difficult to convince healthy people to undergo a blood test. A less invasive technique would allow researchers to collect samples, for instance to track emerging drug resistance in a community.
The test needs to be validated, however. Malaria parasites aren't normally found in urine or saliva, so the researchers don't know why they found the traces of parasite DNA in those samples.
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Waltz, E. Practical malaria tests promise results in remote regions. Nat Med 13, 6 (2007). https://doi.org/10.1038/nm0107-6a