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Diagnostics for Global Health

Mareeg.com- – CORVALLIS, OREGON – In developed countries, most people take for granted that when
they are sick, they will have access to timely diagnosis and treatment. Indeed,
while the diagnostic process – which typically involves sending a sample of blood,
urine, or tissue to a laboratory for analysis – may be cumbersome and expensive,
health-care providers and sophisticated laboratories remain widely available. As a
result, the disease burden in the developed world has declined substantially.

By contrast, in the developing world, millions of people die each year from
treatable diseases like malaria, owing to the lack of sophisticated laboratories and
alternative diagnostic tests. But there is reason for hope: Advances in the field of
microfluidics have the potential to transform health care by allowing “gold
standard” laboratory-based testing to be transferred to the point of care (POC).

A POC test that provides an accurate and timely result would provide diagnostic
access to underserved populations, enabling earlier treatment and helping to avoid
mistreatment (treating another disease with similar symptoms). In order to meet
their potential, however, POC tests must account for the wide range of factors
affecting health-care applications.

First, a POC test must meet the particular environmental and operating constraints
of where it will be used. These may include an unreliable power supply, harsh or
unpredictable environmental conditions, limited contact time between the health-care
provider and patient, lack of user training, severe price constraints, and
inadequate local infrastructure, which can impede the maintenance and repair of
relevant instruments.

Indeed, POC settings can vary from a semi-trained health-care provider working in a
clinic with electricity and access to refrigeration to an untrained individual in an
environment with no mechanism for controlling temperature or humidity. In order to
ensure the broadest coverage possible, POC tests should be designed to work in the
settings with the fewest resources.

Likewise, POC tests must account for different tests’ requirements for clinical
utility. While diagnosing malaria requires only a positive or negative result, an
HIV viral-load test would need to provide a graded output indicating the amount of
virus detected.

One of the most successful POC test formats is that of the well-known pregnancy
test, which requires only the user’s urine and takes roughly 15 minutes to deliver
the result. This class of “rapid diagnostic tests” (RDTs), which are also used for
infectious diseases like malaria and HIV, satisfy many of the key requirements for
global health applications: they are fast and inexpensive, can be conducted easily
by an untrained user, and do not require refrigeration. But they lack the
sensitivity to provide adequate diagnostic information for many health conditions.

Given this, researchers are working to develop more sophisticated paper-based tests.
For example, a new class of device, about the size of a postage stamp, that splits a
sample into multiple zones with different detection chemistries has been used to
test multiple conditions associated with liver failure in HIV and tuberculosis
patients. And “paper network” devices include built-in timing mechanisms to enable
automated multi-step tests like those used in laboratories, but in a disposable
format.

Another mechanism for expanding the capabilities of diagnostic testing would take
advantage of the penetration of mobile-phone networks in developing countries. RDTs
are largely limited to applications that require visual interpretation. A
non-dedicated mobile phone could be used to capture and send image data from an RDT
to a remote site, where a health-care provider would provide feedback on the
results.

But implementing such a program raises a new set of challenges. In order to ensure
accurate test results, the variability of camera positioning by the user and
lighting conditions in different test environments must be addressed. (One promising
approach under development would use an adapter to connect the non-dedicated mobile
phone to the RDT.)

Moreover, a phone-based test would require software infrastructure, such as
communication protocols and prioritization procedures, to coalesce with the
health-care system. And the compatibility issues raised by the wide variety of
mobile-phone handsets would need to be addressed.

Finally, the successful deployment of non-dedicated phone-based testing would
require acceptance from the medical establishment. The US Food and Drug
Administration’s recent approval of several medical devices supported by dedicated
phone-based readers is a promising step.

Effective POC tests are being developed; the proliferation of mobile phones will
further augment the capabilities of these tests. These emergent capabilities promise
to extend the reach of high-quality diagnostics to remote populations, improve
health management, and reduce health-care costs everywhere.

Elain Fu is a professor in the School of Chemical, Biological, and Environmental
Engineering at Oregon State University. Barry Lutz is a professor in the
Department of Bioengineering at the University of Washington.

Project Syndicate, 2013.

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