New breath examination for malaria
The disease-causing parasite may alter compounds humans exhale naturally
People with malaria exhale a distinctive “breathprint,” insights scientists have used to develop a new breath test for diagnosing the killer disease in a group of African children, according to a new study published in the American Society of Tropical Medicine and Hygiene.
The researchers say malaria is a prime candidate for breath-based diagnosis, a conclusion based on past research that shows the disease-causing parasite invades the human body, and may alter compounds humans exhale naturally.
The same technology — enose — could be used to develop a portable malaria breathalyser and breath tests for other diseases as well.
It is the first study to identify a specific set of compounds in human breath that can serve as diagnostic markers for malaria. The analysis is also the first to find that people with malaria exhale a compound identical to a plant-produced vapour that is known to attract mosquitoes, which could be accelerating the spread of disease.
“We were able to determine whether the children were infected based on the composition of six different compounds that were detectable in a sample of their breath,” said Chad Schaber, who presented the results of the study, produced by a team of biologists and bioengineers from Washington University in St Louis in the US. “We took breath samples from 35 children and we correctly determined whether they had malaria — for 29 of them, which is an 83 per cent success rate.”
The researchers say that simple tools like breath-testing for diagnosing malaria are urgently needed — both to direct life-saving treatment to infected individuals and to conduct surveillance as part of a new global push to eliminate and eradicate the disease.
The scientists report that the 83 per cent accuracy rate of their breath test was lower than the 90 per cent or better accuracy of other tests like rapid diagnostic tests or the more labour and technology-intensive method of examining blood samples with a microscope. These blood sample tests are considered the gold standard for malaria diagnosis yet challenging to implement in rural, resource-strapped areas.
Now, the researchers hope to improve the success rate of their breath tests with further refinements to the technology. A similar study had not been done in an area where malaria naturally occurs, they said, where infections are far more intense, or with children, who are more vulnerable to the disease than adults.
To develop a breath test, the researchers recruited 35 children aged three to 15 who had arrived at a paediatric care centre in Lilongwe, Malawi, suffering from fever and other symptoms that could indicate malaria. The children had already been tested for malaria — 17 tested positive and 18 negative. The goal of the study was to determine whether a breath test could be developed that could also distinguish the infected from the uninfected.
The children provided a breath sample by blowing into a simple balloon-like bag. The sample was then pumped into a tube packed with an absorbent material, sealed and sent to a lab at Washington University in St Louis. Researchers also obtained the original blood samples taken from the children at the clinic to further validate the malaria diagnosis by examining them under a microscope. The researchers then determined that malaria infections appeared to alter the concentrations of six different compounds known to naturally occur in human breath.
They used this measure to classify the breath samples as either infected or not with malaria. They then compared the breath diagnosis with the microscopic analysis of blood samples and found the breath test correctly determined malaria status for 83 per cent of the children studied.
“The malaria parasite has been outwitting human interventions for thousands of years, which is why we need these innovative collaborations between biologists and engineers to develop new tools that can give us the upper hand,” said the president of the American Society of Tropical Medicine and Hygiene, Patricia Walker.
A child is tested for malaria. Currently, blood sample tests are considered the gold standard for malaria diagnosis.