Here’s a good reason to start crying with
happiness: your tears could soon save your life by providing an early warning
of cancer, diabetes, and autoimmune disease.
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In the future, they may even predict your risk of developing
Alzheimer’s.
And tears are not the only bodily secretions that are being
used in a new generation of painless diagnostic tests. Scientists say we can
also use earwax, sweat, and nasal mucus to detect everything from depression to
gout.
These newly developed ways to test us for serious conditions
could prevent patients from having to endure trial by needles or scanning
machines.
Take tears — more than mere salty water, the moisture in our
eyes contains precious traces of tell-tale
chemicals circulating in our bodies.
These can be used as markers of illness.
Engineers at
Kobe University in Japan are developing a
device that uses tears to detect breast cancer quickly and easily. The tears
are collected with a strip of paper and then placed in a scanner that examines
them for exosomes, particles that act as couriers between cells, carrying
material such as genes and proteins. For example, if they have come from a
cancer cell, they will be carrying mutated genes and proteins.
The researchers, writing in the Journal of the American
Chemical Society last year, revealed that they had successfully developed
computer-chip technology that found exosome biomarkers of breast cancer in
volunteers’ tears.
"Tear samples can be easily self-collected using a
strip of filter paper," says Professor Toshifumi Takeuchi, the medical
device engineer who led the study.
"Using tears may greatly reduce the
costs of testing and allow much faster detection of cancer malignancies than
mammograms can currently provide."
The device may become available next
year.
Meanwhile, another team of scientists, at Tokyo University,
is using tears to help people with diabetes monitor their blood sugar without
finger-prick tests.
In a study of 100 people with type 2 diabetes, they showed
that the levels of glycoalbumin (a modified protein which reflects the average
blood glucose levels over the preceding two weeks) in tears correlated with the
levels in blood.
The lead researcher, Dr Masakazu Aihara, told the
European Association for the Study of Diabetes last September that they are now
fine-tuning their system for commercial use.
And scientists announced in February that they can use tears
to test for Sjogren’s syndrome, where the immune system mistakenly attacks
glands that produce fluids such as tears and saliva. It also often affects
mucus-secreting glands in the lungs, and can cause inflammation in the kidneys
and nervous system.
Arthritis Research UK estimates that up to half a million
people in the UK have Sjogren’s (typically women, possibly because women’s bodies
regulate inflammation differently). Recent studies have shown that Sjogren’s
also harms a process called autophagy, where our cells clear out damaged
components.
Now scientists at Seoul National University in South Korea
have reported that the amount of ATG5 (a protein involved in autophagy) in
tears may help diagnose Sjogren’s in those with dry-eye symptoms with greater
accuracy than standard diagnostic tests, such as blood tests and skin biopsies.
An accurate test is sorely needed: up to a third of Britons
over the age of 64 suffer with clinically dry eyes, says the
National Institute for Health and Care Excellence.
In a trial of 86 patients who had either Sjogren’s or dry
eyes caused by something else, the ATG5 test was 98.4 percent accurate,
compared with standard test results, which ranged from 81.7 percent to 50.8
percent accuracy.
Anis Barmada, a Cambridge University graduate biology
student who has researched tear analysis, told Good Health that tears may soon
have many more diagnostic applications.
"Tears contain many markers that may be used for
diagnosing a broad array of some of our most common and devastating
diseases," he says. These markers are often found in blood, but are much
more easily obtained from tears.
Researchers are also developing teardrop testing for
Alzheimer’s. Pioneers at Debrecen University in Hungary reported in the journal
PLOS One in 2016 that people developing the disease seem to have tell-tale
protein changes in their tears. Meanwhile, earwax may be an important tool for
diagnosing and monitoring depression and conditions linked to stress.
For years, researchers have been checking levels of the
hormone cortisol to do this — but it’s been difficult to find a fast and easy
method. The most common technique is hair-sample analysis, but this can be
inaccurate.
Now researchers at King’s College London have developed an
earwax cortisol test. Not only is cortisol reliably built up in earwax, the wax
itself effectively preserves it and resists bacterial contamination.
The lead researcher, Dr Andres Herane-Vives, has
invented a self-sampling device similar to a cotton swab, but with a brake that
stops it going too far into the ear and causing damage. Tests on 37 volunteers,
reported in the journal Heliyon in November, showed that earwax samples yield
more cortisol than hair samples. The method may be cheaper, too.
Dr Herane-Vives is now setting up a firm, Trears, to bring
his sampling device to market. He is also investigating whether it could be used
to measure glucose levels in diabetics, and COVID-19 antibodies excreted
in earwax.
Researchers from the US and China, meanwhile, have developed
a new wearable sensor that uses sweat to detect gout-causing compounds. The
thin device contains a laser-etched chemical sensor that identifies uric acid —
high levels of which lead to gout — at concentrations much lower than blood or
urine tests can detect.
Doctors used the sensor to monitor gout patients 24/7. When
levels of uric acid rose sufficiently to threaten a painful attack, the patient
could take preventive anti-inflammatories in good time.
The developer, which reported its success in the journal
Nature Biotechnology two years ago, is now refining the sensor so that it
continuously monitors for signs of cardiovascular disease, diabetes, and kidney
disease.
The only common secretion that scientists aren’t currently
studying for diagnostic potential is our nasal mucus. But we’re missing a
golden opportunity, according to Dr Robert Henkin, who heads Washington DC’s
Taste and Smell Clinic in America.
In 2006, Dr Henkin published a paper reporting that nasal
mucus contains endoglin, a protein also found in blood that is used to detect
the onset of pre-eclampsia, which causes high blood pressure
during pregnancy. Mucus also contains the protein D-dimer, used as an
early warning sign of blood clots in heart disease patients.
Dr Henkin wrote: "A nasal swab test could use nasal
mucus, independent of blood tests, as an inexpensive, safe device to screen
patients worldwide to avoid development of these disorders."
Medicine has ignored this call. Despite delving into tears,
sweat and earwax, it seems that modern medicine is still not ready to pick our
noses.
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