Malaria diagnostic test on a card gives hope for developing
26 January 2009
Researchers at the University of Washington have developed a
prototype malaria test printed on a disposable Mylar card the size of a
credit card. The key to the test is not only miniaturised lab-on-a-chip
technology, but also the use of sugar to keep the dried reagent viable
for months without refrigeration.
Paul Yager, UW bioengineering professor, and colleagues described the
prototype cards in the December issue of the journal Lab on a Chip.
These cards are a critical step in a long-term project funded by The
Bill and Melinda Gates Foundation's Grand Challenges in Global Health
Initiative to develop affordable, easy-to-use diagnostic tools for the
This card is part of a system hoping to diagnose
malaria far from any laboratory. The red circle at the center contains
dehydrated antibodies that can be stored for months without
refrigeration. The lines are tiny channels that guide a blood sample
through the card, and the blood mixes with various solutions for set
periods of time. When the fluids reach the white rectangle, a red spot
will appear, and its intensity shows whether the patient is infected.
Photo credit: Dean Stevens.
"A pivotal issue in having this technology work is making these tests
storable for long periods of time at ambient temperatures," Yager said.
"Normally people work with wet reagents. We're saying we can dry the
reagents down in order to store them without refrigeration. It's the
The malaria cards contain reagents that would normally require
refrigeration, but the researchers figured out a way to stabilize them
in dry form by mixing them with sugar.
Results showed that malaria antibodies dried in sugar matrices
retained 80% to 96% of their activity after 60 days of storage at
The goal of the long-term project is to develop a system with which a
clinician can spot a drop of a patient's blood onto a card and feed it
into an instrument that gives a yes/no answer for a panel of infectious
diseases in 20 minutes or less. Tests with the prototype malaria card
reached a result in less than nine minutes using an immunoassay, or
Developing countries, which are most in need of such technology, face
unique challenges when it comes to medical care.
"Something as seemingly simple as a blood test for a common disease gets
more complicated when money and resources are lacking," said Dean
Stevens, UW bioengineering doctoral student and first author on the
Clinicians trying to diagnose patients in rural, poor communities in
the developing world face hurdles such as unsanitary conditions, lack of
refrigeration for the many common lab tests using ingredients that must
be kept cold, unreliable power and general lack of resources, Stevens
In the developing world, healthcare budgets can be as low as $10 per
person per year, compared to an average of $4,000 in the US. Tests for
diseases also need to be fast and easy to use, because health-care
workers might only have one visit to diagnose and treat a patient, and
thus can't wait days for lab results.
While treatments in poor, rural communities come with their own
difficulties, diagnosis is the key to getting good medical care, Stevens
"Your treatment is really only as good as your diagnosis," he said.
The malaria-test card is being developed as part of an automated
diagnostic system informally called the DxBox, the Dx being medical
shorthand for diagnosis.
The DxBox team is led by Yager and includes UW bioengineering
professor Patrick Stayton; collaborators at PATH, a Seattle-based
nonprofit focused on global health; Micronics Inc. of Redmond, Wash.;
and Nanogen Inc. of San Diego.
The DxBox consists of a portable, fully automatic reader being
developed by Micronics that will process the card-based disposable
tests. The UW prototype cards look for the presence of malarial
proteins, but the team is also working on other kinds of protein tests
as well as a second kind of test for each disease that looks for the
pathogen's DNA or RNA.
The UW's malaria cards use features of common lab tests and take into
account portability, automation and easy storage. The cards rely on
microfluidics, the manipulation of liquids at very small scales. Thin
channels crisscross the Mylar sheets, and syringes are used to pump
different liquids for the tests through the channels. "It's like
plumbing, only the pipes are less than a millimeter wide," Yager said.
Microfluidics not only save space and resources, but working with
liquids on such a small scale allows the researchers to do more. "It's
not just about making big things small," Yager said. "It's also about
doing things that are only possible at that very small scale."
The diagnostic tests in the DxBox system run much faster than
conventional tests in part because the liquids involved behave
differently, a key factor for clinicians who have limited time to spend
with their patients.
Currently, the researchers look for coloured spots on the card that
indicate the presence of malaria proteins. The hue of the colour
indicates the intensity of the disease. The DxBox can read these small
spots automatically, reducing the chance for human error.
While the prototype developed by the UW researchers only tests for
malaria, Yager and his collaborators are working towards cards that also
will test for five other diseases that, like malaria, cause high-fever
symptoms: dengue, influenza, Rickettsial diseases, typhoid and measles.
The "fever panel" of six diseases is merely a starting point, Yager
said. The UW technology could be adapted to include other diseases in
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