Handheld diagnostics: This device rapidily detects tuberculosis, reducing the diagnosis time from a few days to a few hours. Credit: Sionex
Hand-held diagnostics
Portable labs detect tuberculosis and HIV in the developing world
Millions of people in developing countries unknowingly spread HIV and
tuberculosis to one another. A shortage of low-cost diagnostic tools,
allowing people to know that they're infected, is enabling this
epidemic.
Traditional diagnostics require lengthy wait times – a week or more -
for a result and there are few labs in the Third World with reliable
power and trained technicians to analyze samples. Thus, there has been
an emphasis on developing portable lab-on-chip devices that can
speedily diagnose at the point of care. Integrating laboratory
functions on a single chip that can be measured in centimeters or even
millimeters, these devices will allow patients to know their status
almost immediately.
William Rodriguez, an AIDS researcher at Massachusetts General
Hospital, has developed such a device for the purpose of performing a
count of CD4 cells, which are critical to the immune system. The
device can capture these cells from a 10 microliter finger
stick blood sample and deliver a CD4 count within eight minutes. A
patient's CD4 count has enormous implications, helping guide what
therapeutics are used to treat HIV.
Traditionally, CD4 counts have been performed using flow cytometry,
where lasers are used to identify flourescent antibody probes specific
to CD4. Unfortunately, the cytometers can exceed $30,000 in cost.
Rodriguez set out to create a simpler and more affordable diagnostic
method. "It's a handheld instrument that doesn't require anything but
a drop of blood from a fingertip into a card cartridge," said
Rodriguez. "It's built to be more like a glucose meter that anyone can
use in any setting. This gets rid of the optics entirely and does away
with complex handling" of samples.
Developing countries are short on lab personnel capable of performing
flow cytometry – in Malawi, for
example, there are 300,000 patients with HIV and only 13 lab
technicians familiar with the technology. The flow cytometer is "too
complex a machine to be used where the patients are," says Rodriguez."It's a combination of two factors: lack of skilled lab technicians
and the scarcity of high end lab infrastructure."
HIV is just one of the diseases for which low cost diagnostics are
being developed.
Dr. Jose Trevejo, a senior research scientist at the Draper Laboratory
in Cambridge, is developing a handheld device (manufactured by the Draper spin-off company, Sionex) to detect tuberculosis
metabolites in a person's breath. It could reduce the time between
testing and diagnosis from a week to three hours. Current tuberculosis
diagnostics - such as sputum microscopy - require too much time, says
Trevejo. "The delay in delivering an answer needs to be a lot less
than a week," says Trevejo. "If you can't follow up with patients,
they can infect other people. If you could develop a diagnostic that
was point of care for tuberculosis and it was 85% sensitive, it could
save up to 200,000 lives a year globally."
The World Health Organization estimates that 8.8 million people are
infected with tuberculosis annually, including 2.5 million new cases
in Africa and 2.9 million in Southeast Asia. It is impractical to
operate laboratory equipment in these areas of the world, so Trevejo's
device could prove extremely useful. The Foundation for Innovative and
New Diagnostics, in part funded by Microsoft's Bill Gates, is
currently looking into funding development of the device.
