A cheap, portable blood test kit that requires only a finger prick of blood, and can tell in minutes if you have HIV or syphilis, has proved successful in field tests in Rwanda. The biomedical engineers behind the “lab on a chip” device that can carry out complex laboratory assays in situ, hope it will streamline blood testing and revolutionize medical care around the world, especially in remote regions where the costs of sending off for complex lab work are prohibitive. They publish the first field results of their integrated microfluidic-based diagnostic device in the 31 July online issue of Nature Medicine.
Study leader Samuel K Sia, assistant professor of biomedical engineering at Columbia University, New York, told the press:
“We have engineered a disposable credit card-sized device that can produce blood-based diagnostic results in minutes.”
“The idea is to make a large class of diagnostic tests accessible to patients in any setting in the world, rather than forcing them to go to a clinic to draw blood and then wait days for their results,” he added.
The lab on a chip is based on ideas from studying microfluidics and nanoparticles, which Sia and colleagues brought together in a novel way to produce a low-cost diagnostic device that can manipulate small amounts of fluid.
The device is called “mChip” (short for mobile microfluidic chip) and needs only a tiny amount of blood, as much as comes from pricking your finger. Even newborns can be tested. And within 15 minutes, it gives quantitative, objective results that do not need to be interpreted by a user, thus significantly cutting the delay between testing and treating patients.
The mChip device Sia and colleagues used in the study replicates all the steps of “enzyme-linked immunosorbent assay” or ELISA, a biochemical method that looks for antigens or antibodies in a sample. The main advantage is the much lower total material cost.
The device contains a microchip and a miniature version of test tubes and chemicals. The chip costs about $1 and the whole kit about $100.
The authors write:
“The chip had excellent performance in the diagnosis of HIV using only 1 [micro-litre] of unprocessed whole blood and an ability to simultaneously diagnose HIV and syphilis with sensitivities and specificities that rival those of reference benchtop assays.”
Sia and colleagues carried out the field tests in Rwanda. For four years they partnered with Columbia’s Mailman School of Public Health and three local non-government organizations in Rwanda to trial the mChip with hundreds of patients.
The chip showed 100% detection of HIV-positive cases, and only one false positive in 70 samples. In dual tests of HIV and syphilis, the detection rate for syphilis was 94% with only four false positives out of 67 samples. These results are comparable with lab tests, say experts.
Rosanna Peeling, a diagnostics researcher at the London School of Hygeine and Tropical Medicine, was not part of the study. She told the Washington Post that the new test “can be done outside the lab with all the same advantages and sensitivity,” as the more expensive and time-consuming laboratory analysis that many people in developing countries currently rely on.
Sia said he hopes to use the mChip to help pregnant women in Rwanda who, because they live in remote regions and can’t visit a hospital or clinic with a lab, have no reliable way of finding out if they have AIDS and sexually transmitted diseases.
Sia said the medical challenge in helping the Rwandan women, and others like them in the poorest regions of the world, is reliable diagnostics. Without reliable diagnostics, despite having a range of drugs available, field medical workers don’t know which treatments to give.
Sia co-founded a company, Claros Diagnostics in 2004. The company, which MIT Technology Review recently named one of the 50 most innovative in the world, and Sia’s lab at Columbia Engineering worked together to develop the mChip.
Claros Diagnostics has already developed a version of mChip that diagnoses prostate cancer. The device was approved for use in Europe in 2010.
The innovation is an elegant example of what happens when engineering and life sciences come together to tackle a pressing public health problem.
Sia is also working on new tools to control the environment around human cells to find out how they interact to produce tissue and organs. To make the high-resolution tools, he and his team are drawing on skills and ideas from fields as diverse as microfabrication, microfluidics, materials chemistry, biochemistry, molecular biology, and cell and tissue biology.
Written by Catharine Paddock, PhD