Dr Yousef carries out sampling, to trap tell-tale disease molecules
from the subject’s breath
Scientists in the UK and US - in two separate studies - have shown that
various diseases such as diabetes, asthma and cancer can be detected by
merely checking a person’s breath.
The
researchers at UK’s Swansea University - for their part - are using
“GCMS-TD” (gas chromatography, mass spectrometry and thermal
desorption) technology to analyse the concentrations of “Volatile
Organic Compounds” (VOCs) in breath.
Whereas the team of US
scientists at JILA, a joint institute of the National Institute of
Standards and Technology (NIST) and the University of Colorado (CU),
have shown that by sampling a person’s breath using “optical frequency
comb spectroscopy” they can detect molecules in the breath that may be
markers for diseases.
How the technology works
Every
time we breathe in, we inhale a mixture of gasses – mostly nitrogen,
oxygen, carbon dioxide, and water vapour, but also traces of other
gasses, such as carbon monoxide, nitrous oxide, etc.
Each time
we exhale, we blow out a slightly different mixture with less oxygen,
more carbon dioxide, and a rich collection of more than a thousand
types of other molecules – most of which are present only in trace
amounts.
Some of these tracer breath molecules are biomarkers of
disease. Just as bad breath may indicate dental problems, excess
methylamine can be used to detect liver and kidney disease, ammonia on
the breath may be a sign of renal failure or hepatitis, elevated
acetone levels in the breath can indicate diabetes, dimethyl sulphide
is linked to cirrhosis, and nitric oxide levels can be used to diagnose
asthma.
When many breath molecules are detected simultaneously, highly reliable and
disease-specific information can be collected.
Research In the United Kingdom…
“Studies
have shown that high concentrations of certain VOCs in breath can
correlate with disease,” said Dr Masood Yousef, a senior research
assistant at Swansea. “If unique markers for diseases can be recognised
earlier than traditional techniques, then there is a potential to
diagnose disease before any symptoms have developed, and without the
need for invasive procedures.”
The GCMS-TD system works by
analysing all the chemicals and compounds that make up a patient’s
breath. It creates a breath profile, which allows scientists to
identify VOCs that may signify the presence of disease.
Dr
Yousef believes that the breath test will provide a more convenient
method for diagnosing serious diseases than blood or urine analysis.
It
is hoped that the research in Swansea will lead to the development of
diagnostic tools such as test strips that give positive results for
specific illness markers.
... and In the United States
While
many studies have been done to showcase the potential of optical
technologies for breath analysis, the JILA approach takes an important
step toward demonstrating the full power of optics for this prospective
medical application.
“Our technique – called cavity-enhanced
direct optical frequency comb spectroscopy – can give a broad picture
of many different molecules in the breath all at once,” said research
leader Jun Ye, a fellow of JILA, NIST and a professor at Colorado
University’s Department of Physics.
“Optical comb spectroscopy
is powerful enough to sort through all the molecules in human breath,”
Ye said, “but it is also sensitive enough to find those rarest
molecules that may be markers of specific diseases.”
In the
experiments performed by Ye and his colleagues, the technique was used
to analyse the breath of several student volunteers.
The
researchers had the students breathe into an optical cavity – a space
between two standing mirrors. The optical cavity was designed so that
when they aimed a pulsed laser light into it, the light bounced back
and forth so many times that it covered a distance of several
kilometres by the time it exited the cavity. This essentially allowed
the light to sample the entire volume of the cavity, striking all the
molecules therein.
In addition, this lengthens the light-molecule interaction time thereby
increasing the sensitivity.
By
comparing the light coming out of the cavity to the light that went in,
Ye and his colleagues could determine which frequencies of light were
absorbed and by how much. This information allows them to sensitively
identify many different molecules.
>From labs to dispensaries
While
the efficacy of these techniques has yet to be evaluated in clinical
trials, monitoring the breath for such biomarkers is an attractive
approach to medicine because breath analysis is the ultimate
non-invasive and low-cost procedure.
“Breath samples are much
easier to collect than blood and urine,” Dr Yousef said. “They can be
collected anywhere by people with no medical training, and there are no
associated biohazard risks.”
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