New test to identify people from sense of smell

Scientists have developed an 'olfactory fingerprint' test that may not only help identify individuals but also quickly detect diseases such as Parkinson's and Alzheimer's.
Each person has, in their nose, about six million smell receptors of around four hundred different types.
The distribution of these receptors varies from person to person - so much so that each person's sense of smell may be unique.
Scientists at the Weizmann Institute of Science in Israel report on a method of precisely characterising an individual's sense of smell, which they call an "olfactory fingerprint."
The implications of this study reach beyond the sense of smell alone, and range from olfactory fingerprint-based early diagnosis of degenerative brain disorders to a non-invasive test for matching donor organs.

The method is based on how similar or different two odours are from one another. In the first stage of the experiment, volunteers were asked to rate 28 different smells according to 54 different descriptive words, for example, "lemony," or "masculine."

The experiment, led by Dr Lavi Secundo, with Kobi Snitz and Kineret Weissler, members of the lab of Professor Noam Sobel of the Weizmann Institute's Neurobiology Department, developed a complex, multidimensional mathematical formula for determining, based on the subjects' ratings, how similar any two odours are to one another in the human sense of smell.
The strength of this formula, according to Secundo, is that it does not require the subjects to agree on the use and applicability of any given verbal descriptor.

Thus, the fingerprint is odour dependent but descriptor and language independent.
The 28 odours make for 378 different pairs, each with a different level of similarity. This provides us with a 378-dimensional fingerprint.
Using this highly sensitive tool, the scientists found that each person indeed has an individual unique pattern - an olfactory fingerprint.
The researchers said their computations show that 28 odours alone could be used to "fingerprint" some two million people, and just 34 odours would be enough to identify any of the seven billion individuals on the planet.
The research also suggested that our olfactory fingerprint may tie in with another system of ours in which we all differ - the immune system.

They found, for example, that an immune antigen called HLA, today used to assess matches for organ donation, is correlated with certain olfactory fingerprints.
Researchers think that olfactory fingerprinting, in addition to helping identify individuals, could be developed into methods for the early detection of diseases such as Parkinson's and Alzheimer's, and it could lead to non-invasive methods of initial screening as to whether bone marrow or organs from live donors are a good match.
The study was published in the journal PNAS.