Grisalea Uwabaho does not know her daughter’s result yet, but – whatever it is – she says she will believe it.

The 30-year-old mother of five walked an hour this morning to bring her youngest child – her wailing, feverish one-year-old daughter, Mariam – to this tin-roofed, two-room clinic, which is the most advanced health facility she could hope to reach in Kyankwanzi district, an impoverished corner of central Uganda. Uwabaho fears that her baby may have malaria, and she has brought her here to find out for sure.

A nurse pricks the baby’s finger then places a drop of her blood on a tiny window inside a small strip of plastic. Fifteen minutes later, he announces the result: negative. the nurse gives Uwabaho medicine to fight off Mariam’s cough and diarrhoea.

Here in Kyankwanzi district, and across sub-Saharan Africa, that little strip of plastic – better known as a rapid diagnostic test (RDT) for malaria – is revolutionising both the management and the understanding of a disease which threatens nearly half of the world’s population and that killed close to 800,000 people in 2009, 90% of them in Africa. Clinicians in far-flung African villages used to have no choice but to diagnose malaria based on symptoms alone. But, today, health workers who have access to RDTs – which now cost less than $1 (63p) apiece – can determine with relative certainty whether patients have any malaria parasites in their blood.

It is a simple feat, perhaps, but it represents a crucial step in the struggle to control this deadly, but highly treatable, disease. where they have been introduced, RDTs have helped to improve patients’ chances of recovery by ensuring more appropriate treatment for fever-causing conditions and conserving precious anti-malarial drugs. they have also helped to paint a much more accurate picture of the malaria problem the world faces today.

“As RDTs were introduced, it became clear that there was nowhere near as much malaria in many areas as people thought,” says Dr David Bell, the head of the malaria diagnostics programme at the Geneva-based Foundation for Innovative new Diagnostics (Find).

“Everyone who had a fever used to be classified as having malaria, and now maybe 20% of those people have malaria, and 80% have something else,” he says. People have to start thinking differently about the importance of accurate diagnosis, he says.

Thanks to an upsurge in funding, the global struggle to control malaria has made significant progress in the past 10 years. according to the Roll back Malaria Partnership, an umbrella organisation based in Geneva, global deaths from the disease have dropped 38% since 2000. the RDT, despite only being around for a few years, is now playing a very significant part in the continuing control of malaria.

Such is the power and accuracy of the little plastic strip that, in 2010, the World Health Organisation (WHO) did away with its longstanding recommendation that malaria should be treated based on clinical symptoms alone. Now, it says that health workers everywhere – even in sub-Saharan Africa, where conditions are most challenging – should aim for parasite-based diagnosis, either with an RDT or a microscope, the traditional and much more technically demanding method of detecting malarial parasites.

When WHO changed its official recommendation, many countries followed suit; Uganda was one of them. Health officials there have set an ambitious target: by 2015, they want 85% of all suspected malaria cases to be subjected to parasite-based diagnosis. In 2007, that figure stood at just 9%; four years later, it has nearly trebled to 25%.

The recent gains have come in part thanks to the work of the Malaria Consortium, a UK-based international NGO that has been supplying RDTs and working with the Ministry of Health to teach health workers how to use them in five districts in central and western Uganda. the organisation’s work has revealed both the advantages and the challenges of the tests; their experience holds critical lessons for others looking to promote the use of RDTs.

Getting the local health workers to change their attitudes has been one of the trickiest aspects of the project, says Robin Altaras, who co-ordinates Malaria Consortium’s Comic-Relief-funded Pioneer project in Uganda.

“They’ve gone from 20 years of practising presumptive treatment of malaria to suddenly radically changing how they manage fever,” he says. “That’s a process that needs to be supported continuously over the long term, starting with training and following with supervision.”

The particular brand of test that Malaria Consortium has chosen – one of only two the Ugandan government has approved for use – has a shelf life of two years, in common with all RDTs, and a sensitivity rate of 97%, according to ongoing product evaluations by WHO and Find. this makes it one of the best of the dozens of RDTs currently available.

When used correctly, Altaras says, RDTs can serve as a powerful control on drug stocks, reducing wastage by limiting anti-malarial medicines to only those patients who truly need them. That means that clinics are less likely to run out of stock; it also means that the medicines are more likely to remain effective in the long run.

Experts say it may only be a matter of time before the highly adaptable malaria parasite evolves to outsmart the compound artemisinin, which is currently the best – and last – line of defence against the disease. Handing out fewer courses of those precious artemisinin-based combination therapies (ACTs) – which can cure a person of malaria in just three days – means slowing down the clock on the ticking timebomb of resistance.

“ACTs should be taken only by those who have parasites, who have test results showing positive,” says Agaba Bosco, who is in charge of malaria diagnostics for Uganda’s National Malaria Control Programme. “The biggest threat now is the potential development of drug resistance,” he says, adding that such a scenario “would be a disaster” for malaria control.

A disaster in Uganda, and a disaster around the world. That is one more reason, experts say, why the global public health community should sharpen its focus on diagnostics.