HEALTH: Medical diagnostics approaches the final frontier
Struggling with blood tests in rural areas may become a thing of the past
JOHANNESBURG, 16 December 2011 (IRIN) - In the popular 1960s science fiction TV series Star Trek, set in the 23rd century, a handheld medical “tricorder” scans a person’s internal body organs for the presence of any infections, providing an instant diagnosis.
Fast forward to today and imagine a handheld device powered by batteries that can take a drop of blood, urine or sputum and tell a community health worker in a remote village whether a feverish child has malaria, dengue or a bacterial infection.
That is the kind of device, Peter Singer, professor of medicine at the University of Toronto and executive officer of Canadian government-funded non-profit Grand Challenges
, says his organization, along with the Bill and Melinda Gates Foundation, is aiming to help scientists develop.
The two organizations have invested around US$32 million in the discovery and development of new and improved diagnostic tools to help health workers in developing countries, with the aim of speeding up treatment and saving lives.
“Diagnosis is the neglected cousin of prevention and treatment,” said Singer, explaining his interest in diagnostic tools. “More rapid diagnosis of malaria alone could prevent 100,000 deaths a year. We believe this and other life-saving opportunities are within our reach. We think we can have a device like the medical `tricorder’ in 6-7 years."
Grand Challenges is currently on the lookout for innovative diagnostic tools and processes covering the collection and preparation for analysis of biological samples, disease identification, technology to obtain and transmit data and receive results, and robust devices which work in the field where there is often no electricity or refrigeration.
Funding has been provided for the development of a handheld analyser which can detect not only whether a person has malaria but also the kind of parasite involved, and the proportion of red blood cells infected (indicating the severity of the infection).
Called a mini-PCR (Polymerase Chain Reaction), the device identifies malaria from its DNA fingerprint.
The World Health Organization says this technique is more accurate than microscopy in detecting malaria, and Chandrasekhar Nair, director of Bigtec Labs in India which developed the mini-PCR analyser, said it does all the processing that a specialized laboratory would do at a fraction of the cost.
The machine can be operated by a community health worker, he said. A sample of blood is placed in a port on a microchip, which is inserted into the device. The microchip has a memory of the DNA of all the possible malaria pathogens. It compares the DNA fingerprint of the sample with those in its memory and displays the result on the screen.
If the diagnosis is “malaria”, the device indicates this on the screen along with a numerical ranking of its severity. Results can also be transmitted via a mobile phone attached to the device.
The entire process takes little more than an hour, said Nair, adding that tests showed the machine was as accurate as a commercial bench-top PCR system used in laboratories.
Although malaria can be detected in 15 minutes by the Rapid Diagnostic Test (RDT), it only picks up whether a person is infected with plasmodium falciparum (fatal malaria) or one of the other three species of human malaria.
The Centers for Disease Control and Prevention
points out that the RDT does not eliminate the need for malaria microscopy. “The RDT may not be able to detect some infections with lower numbers of malaria parasites circulating in the patient’s bloodstream. Also, there is insufficient data available to determine the ability of this test to detect the two less common species of malaria, P. ovale and P. malariae. Therefore, all negative RDTs must be followed by microscopy to confirm the result.”
Bigtec’s Nair said they were also developing disease-specific microchips for dengue and chikungunya, typhoid, H1N1 and hepatitis B.
Bigtec is using the grant money to develop a sophisticated filter to concentrate pathogen DNA from samples of blood, sputum, urine, or nasal and throat swabs. Once concentrated, the DNA can be processed and illnesses identified by the mini-PCR.
A cloth which detects disease
Other innovative tools have also won grants. One example is a piece of woven fabric which can test blood or urine for disease: Different varieties of silk yarn are coated with antibodies or other chemicals before being woven into a multi-zone fabric in one simple step. The fabric is then cut into thin strips for individual tests, analogous to home pregnancy tests, explained Dhananjaya Dendukuri from Achira Labs in India, who developed the concept with Nandini Dendukuri from McGill University in Montreal.
As the sample becomes wet it changes colour providing a visual readout.
Dendukuri said the cost of using the silk cloth or Fabchip will be comparable to that of wooden sticks used to detect diabetes from urine samples. A number of tests can be conducted on a single piece of cloth.
Scientists working on the Fabchip have yet to conduct field trials.
"We hope these innovative ideas lead to technologies that allow patients to get the right treatment, quickly speeding recovery, limiting the spread of disease, and helping them to lead healthy, productive lives," said Chris Wilson, director of Global Health Discovery at the Bill & Melinda Gates Foundation, adding: "Safe, effective methods of diagnosing illness at the point of care are vital to improving health in developing countries."