8 March 2014
Last updated at 21:47 ET
"I may sound crazy but I'm not," writes Joanie, on an online
support forum for people affected by cancer. She relates how, while her
husband suffered from prostate cancer, she could smell "an odour similar
to decay". It went away with the cancer, but in 2012 she was alarmed to
smell the putrid stench once again. Not long afterwards, Joanie herself
was diagnosed with lung cancer.
Although many cancer sufferers and their relatives do not notice a nasty smell, Joanie's experience is not unusual. "I've had numerous people writing to me about this," says George Preti from the Monell Chemical Senses Center in Philadelphia. "I've had lots of notes from nurses and researchers in the area, but they're mostly anecdotal reports."
Throughout history, doctors have sniffed their patients' breath, urine, stool and other bodily fluids to help with diagnoses. A 2011 review article featured "smelling notes" of dozens of diseases. Yellow fever is said to smell like a butcher's shop, liver failure like raw fish, and typhoid like freshly baked brown bread.
A recent experiment also provides some evidence that people give off a bad smell as they fall sick.
Although Olsson admits that the study - published in the
journal Psychological Science - was very small, he believes ill people
may emit a chemical "cue" to warn others of contagion, or possibly to
signal they need help. Bad smells exist for a reason, agrees Val Curtis
from the London School of Hygiene & Tropical Medicine. "The disgust
system in the brain has evolved to make us stay away from things that
might make us sick. The most dangerous place on the planet is other
people."
For Mats Olsson, "the new thing and interesting thing" about
his T-shirt study is that human beings seem capable of sniffing out
disease early on - long before we start smelling like a butcher's shop
or raw fish.
For cancer, early detection is crucial, but the symptoms that prompt a visit to the doctor's surgery often don't emerge until the disease is advanced. George Preti gives the example of ovarian cancer, which has become the focus of his own work. "If you picture a peppercorn and an onion, the difference in size between those two is the difference between when it should be diagnosed and when it's traditionally diagnosed," he says.
He hopes that ovarian cancer's smell could help doctors arrest the disease at the peppercorn stage. As part of everyday metabolism, our bodies produce chemicals which evaporate into the air. Cancerous cells, Preti says, have a different metabolism from normal cells, and therefore emit a different pattern of chemicals, a different odour. While it's too subtle for most human noses, dogs have been trained to identify multiple types of cancer, as well as diabetes. (Humans have around five million scent receptors, but dogs have up to 300 million.)
Preti is working with the Penn Vet Working Dog Center, which is
training four dogs to detect ovarian cancerous tissue. He says they can
do this with greater than 90% accuracy. However, the idea is not that
these dogs will get jobs in the oncology departments of hospitals.
Instead, the Penn Vet dogs will help Preti identify the unique "odour
signature" of ovarian cancer. "They're sort of a four-legged bio-assay,"
he says.
Once the odour signature or profile of ovarian cancer is determined, it will be used by Preti's colleague Charlie Johnson to program sensors in a device sometimes called an "electronic nose" or "e-nose". Johnson's prototype mimics the receptors in our nose with hundreds of carbon nanotubes, each with a strand of DNA attached. These strands are able to transpose the mix of chemicals in the air into an electronic signal. "You can have the power of a dog's nose on this small chip the size of your fingernail," Preti says. It's this device, rather than the dogs, that might end up on hospital wards.
But dogs aren't the only animals that can smell cancer. So, apparently, can fruit flies. A recent paper in Nature showed that the scent of cancer samples prompted a particular pattern of activity on the flies' antennae. The paper's author, Martin Strauch at the University of Konstanz in Germany, is planning to identify which receptors on the antennae respond to the cancerous smells. Then he hopes to grow his own antennae in a petri dish, for use in an e-nose. "The biological sensors have been optimised by evolution - they are quite good," he says.
The device, developed by a company called Menssana, starts by
building a profile of the ambient gas in a room. A patient in the room
then breathes into a tube for two minutes. The composition of her breath
is laid over the ambient room profile, and whatever's left over is
compared to the known profile for breast cancer held in a database in
the US. The results of the latest tests on BreathLink show it has
similar diagnostic power to a mammogram, but women don't have to undress
and are not exposed to X-rays.
The results also come through within 10 minutes, instead of two
weeks. Dr Roy Lalisang, who tested the machine at the University of
Maastricht Medical Centre in Holland, says further tests are required,
but it could be ready for service in the next couple of years.
BreathLink could also, potentially, be used to test for tuberculosis.
Another company, Owlstone, also hopes to bring a device to market in roughly the same time-frame, which would be used to screen patients for bowel cancer and other digestive diseases. Called Lonestar, this device would prevent some patients having to undergo an uncomfortable colonoscopy.
As well as screening patients, medical sniffing devices can
potentially be used to monitor the patients, as well as screening them.
Krishna Persaud at the University of Manchester has been testing one
that monitors victims of severe burns for signs of infection - if his
e-nose sniffs an unwelcome odour, doctors can react immediately, instead
of waiting three days for the sample to be analysed in a lab.
For lots of patients these new tools cannot arrive in hospitals and doctors' surgeries too quickly.
Roy Lalisang says that since the results of the BreathLink study were published last Wednesday his phone has not stopped ringing - most of the callers being women who are sick of getting prodded and pummelled in mammograms.
"In my daily practice, I so frequently hear from women who have to undergo mammography," he says. "They say, 'Oh, when is the next one? In one year? Is it really necessary because it's so painful!' I always say: 'If men had to undergo this examination they would have found another test many years ago.'
"Women will not undergo mammography if this is a comparable screening test."
Mats Olsson spoke to Health Check on the BBC World Service. Listen to the programme on iPlayer or get the Health Check podcast.
Follow @BBCNewsMagazine on Twitter and on Facebook
Sniffing out cancer with electronic noses
We
may soon be able to obtain easy and early diagnoses of diseases by
smell. This week researchers found one odour-sniffing machine was as
good as a mammogram at detecting breast cancer - and many other devices
capable of spotting other diseases may be on the way.
Although many cancer sufferers and their relatives do not notice a nasty smell, Joanie's experience is not unusual. "I've had numerous people writing to me about this," says George Preti from the Monell Chemical Senses Center in Philadelphia. "I've had lots of notes from nurses and researchers in the area, but they're mostly anecdotal reports."
Throughout history, doctors have sniffed their patients' breath, urine, stool and other bodily fluids to help with diagnoses. A 2011 review article featured "smelling notes" of dozens of diseases. Yellow fever is said to smell like a butcher's shop, liver failure like raw fish, and typhoid like freshly baked brown bread.
What diseases smell like |
||
|---|---|---|
| Disease | What to smell | Aroma |
|
Source: Alphus D. Wilson, Manuela Baietto, "Advances in
Electronic-Nose Technologies Developed for Biomedical Applications",
published in Sensors |
||
|
Anaerobic infection |
Skin, sweat |
Rotten apples |
|
Bladder infection |
Urine |
Ammonia (window cleaner) |
|
Diabetes |
Breath |
Acetone-like (nail polish remover) |
|
Liver failure |
Breath |
Raw fish |
|
Rubella |
Sweat |
Freshly plucked feathers |
|
Schizophrenia |
Sweat |
Mildly acetic (vinegar) |
|
Scrofula |
Body |
Stale beer |
|
Typhoid |
Skin |
Freshly baked brown bread |
|
Yellow Fever |
Skin |
Butcher's shop |
Continue reading the main story
Find out more
- Mats Olsson spoke to Health Check on the BBC World Service.
A team led by Mats Olsson at the
Karolinska Institute in Stockholm dressed eight healthy volunteers in
tight cotton T-shirts and injected one half of the group with a placebo
and the other half with a chemical that gave them a mild flu-like
reaction. A month later, the participants came back and were injected
with the other solution - the one they had not received the first time. All
the T-shirts were then collected and patches from the underarm area
were cut out and placed in squeeze bottles. These were used to supply
puffs of air to a panel of smelling volunteers. "They rated the T-shirts
with regards to intensity, unpleasantness and healthiness," says
Olsson. "And for all these measures it turned out that the so-called
sick group smelled more aversively."
A dog's nose being harnessed for cancer research
For cancer, early detection is crucial, but the symptoms that prompt a visit to the doctor's surgery often don't emerge until the disease is advanced. George Preti gives the example of ovarian cancer, which has become the focus of his own work. "If you picture a peppercorn and an onion, the difference in size between those two is the difference between when it should be diagnosed and when it's traditionally diagnosed," he says.
He hopes that ovarian cancer's smell could help doctors arrest the disease at the peppercorn stage. As part of everyday metabolism, our bodies produce chemicals which evaporate into the air. Cancerous cells, Preti says, have a different metabolism from normal cells, and therefore emit a different pattern of chemicals, a different odour. While it's too subtle for most human noses, dogs have been trained to identify multiple types of cancer, as well as diabetes. (Humans have around five million scent receptors, but dogs have up to 300 million.)
MacBane, a dog at the Penn Vet Working Dog Centre, can identify samples of tissue containing ovarian cancer
Once the odour signature or profile of ovarian cancer is determined, it will be used by Preti's colleague Charlie Johnson to program sensors in a device sometimes called an "electronic nose" or "e-nose". Johnson's prototype mimics the receptors in our nose with hundreds of carbon nanotubes, each with a strand of DNA attached. These strands are able to transpose the mix of chemicals in the air into an electronic signal. "You can have the power of a dog's nose on this small chip the size of your fingernail," Preti says. It's this device, rather than the dogs, that might end up on hospital wards.
But dogs aren't the only animals that can smell cancer. So, apparently, can fruit flies. A recent paper in Nature showed that the scent of cancer samples prompted a particular pattern of activity on the flies' antennae. The paper's author, Martin Strauch at the University of Konstanz in Germany, is planning to identify which receptors on the antennae respond to the cancerous smells. Then he hopes to grow his own antennae in a petri dish, for use in an e-nose. "The biological sensors have been optimised by evolution - they are quite good," he says.
Continue reading the main story
Rat detectives
- In Mozambique and Tanzania, the charity Apopo trains rats to detect tuberculosis
- TB is diagnosed by microscopy, but inadequate analysis in these countries means fewer than half of infected samples are identified
- The rats act as a second line of defence, double-checking mucus samples deemed to be clean of TB
- The rats have discovered more than 5,000 cases of TB so far
- The charity also uses its "HeroRATs" to sniff out landmines
Electronic noses of other kinds
are already being put to work in a range of different fields, from
checking for poison gas in war zones to ensuring the quality of beer.
They are now on the verge of being set medical tasks, following tests on a device called BreathLink, which is designed to check for breast cancer.
Menssana's BreathLink technology being tested at Maastricht UMC
Another company, Owlstone, also hopes to bring a device to market in roughly the same time-frame, which would be used to screen patients for bowel cancer and other digestive diseases. Called Lonestar, this device would prevent some patients having to undergo an uncomfortable colonoscopy.
Owlstone's spectrometer chip - the heart of its e-nose technology
Continue reading the main story
E-noses can look for...
- taints in pharmaceuticals
- poison gas or chemical weapons
- contamination of food and drinks
- unwanted chemicals produced in oil extraction
- sewage building up
- fish that have gone off
- chemicals that can lead to antique manuscripts degrading
A long-term goal for the sector
is to get easy-to-use diagnostic tools into the home... and into our
pockets. With the ever-growing sophistication of mobile phones - some of
the latest models have temperature and humidity sensors - the idea of
routinely breathing on to your phone to check for disease is not science
fiction. The chip already exists, and getting it into a phone is
straightforward engineering or electronics, says Billy Boyle of
Owlstone, which was a recent runner-up in a competition sponsored by Nokia.
Roy Lalisang says that since the results of the BreathLink study were published last Wednesday his phone has not stopped ringing - most of the callers being women who are sick of getting prodded and pummelled in mammograms.
"In my daily practice, I so frequently hear from women who have to undergo mammography," he says. "They say, 'Oh, when is the next one? In one year? Is it really necessary because it's so painful!' I always say: 'If men had to undergo this examination they would have found another test many years ago.'
"Women will not undergo mammography if this is a comparable screening test."
Mats Olsson spoke to Health Check on the BBC World Service. Listen to the programme on iPlayer or get the Health Check podcast.
Follow @BBCNewsMagazine on Twitter and on Facebook
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