About 40 per cent of malaria cases are not diagnosed, which not only presents a major threat to public health but also hampers efforts to eliminate the disease.

Accurate, robust tests that are cheap enough for widespread use in some of the poorest countries of the world are urgently needed, according to Dr Iveth González, head of malaria at FIND, a Geneva-based not-for-profit organization focusing on diagnostics for diseases of poverty.

"One of the issues is people beyond the reach of public health centres who seek care in private clinics or pharmacies where they don't do tests, they just sell treatments," Dr González says.

The symptoms of malaria - including, most frequently, fever - are very similar to a number of other conditions, which makes clinical diagnosis difficult. In addition, many people are infected with the malaria parasite but show no symptoms at all, while still spreading the disease.

Recent action by the World Health Organisation has improved matters, Dr González says. "In 2010 there was a new recommendation from WHO to give treatment only to malaria cases confirmed by microscopy or the malarial rapid diagnostic test (RDT). This recommendation was supported by the WHO and FIND evaluation programme to demonstrate the quality of RDTs, which also increased the confidence of health care workers and their patients in the RDT results. The great success of RDTs is that they don’t need any extra equipment and are easy to use even in remote areas.”

Progress is being made in the public health arena but many people in areas where malaria is endemic live too far from a health centre and must rely on local private providers who may not use RDTs to confirm a malaria diagnosis.

The lack of accurate diagnostic tools also risks misdiagnosing other causes of fever, so viral infections may be treated with antibiotics, which increases the spread of antibiotic resistant bacteria, Dr González points out.

Better diagnostic tools will also help the battle to eliminate malaria. "We need even better diagnostic tests because one of the strategies for eliminating malaria is to treat any infection, meaning we are also aiming to treat patients without any kind of symptoms but still capable of transmitting the disease, so for that we need highly sensitive diagnostic tools," she says. "We also need better diagnostics for surveillance to get very good data to demonstrate that malaria really is going down."

Genetic tests promise the capability of detecting very low levels of infection that are not detected with current tests. "There are molecular tests that amplify genetic material from the parasite so they are able to detect very low-level infections that are not detected by microscopy or current RDTs," Dr González says. "We now need to develop diagnostic tools that are robust enough for use in remote settings and don't need to be refrigerated."