OT: Earwax for diagnosing disease

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I have had so many blood tests that sometimes I feel like a pincushion.

Apart from the count of different types of blood cells, the results from the blood tests are of water-soluble components (e.g. electrolyes, glucose, lipids that are kept in solution by proteins, etc.). Standard blood tests don’t analyze water-insoluble (hydrophobic) components.

(As an aside, when blood components become insoluble they tend to deposit onto surfaces like the cholesterol and calcium that deposit inside blood vessels and heart valves.)

The gold standard for diagnostics is a test that is more sensitive and specific than a physical exam and that is non-invasive.

What about diseases that cause changes in lipid metabolism? It’s not easy to analyze lipids because many of them have high molecular weight so they aren’t volatile. (They don’t evaporate easily so gas chromatography can’t be used.) They can be separated by HPLC (high pressure liquid chromatography) but this is typically used in research labs and not high-throughput medical diagnostic labs. Other hydrophobic compounds are volatile organic compounds (VOCs) which can be analyzed by gas chromatography.

One amazing example is the production of specific lipids that are produced in sebum (an oily secretion from specific sweat glands) by people with Parkinson’s Disease. This was first detected on her husband by a nurse with an incredibly acute sense of smell. There is potential for sebum analysis to be a biomarker for PD.

Like sebum (the oily component of sweat), cerumen (earwax) can carry hydrophobic molecules that may change with disease states.

“In the future, we hope that the cerumenogram will become a routine clinical examination, preferably every six months, that allows, with a small portion of earwax, to simultaneously diagnose diseases such as diabetes, cancer, Parkinson’s, and Alzheimer’s, as well as evaluate metabolic changes resulting from other health conditions,” says Antoniosi Filho, a Brazilian scientist.

https://www.nature.com/articles/s41598-019-48121-4

This study used Headspace/Gas Chromatography-Mass Spectrometry (HS/GC-MS) - a common technique found in many analytical laboratories around the world. Their analysis of cerumen volatile compounds, which they called a “cerumenogram,” was able to distinguish 100% between people with and without cancer. Note that this technique analyzed Volatile Organic Compounds which are easier to separate than non-volatile compounds.

As a chemist, I find this fascinating. The subtle alterations in metabolism caused by diseases (some in the mitochondria) can be detected and analyzed much earlier than the gross physical signs of disease. The techniques use very tiny samples that are non-invasive. There’s a huge difference between using a Q-tip to get an earwax sample and a spinal tap (which is currently used to diagnose Alzheimer’s Disease).

Early detection and early treatment. Great micro-chemistry. New understanding of metabolic changes in disease states.

This is real progress. It isn’t clinically available yet but they’re working on it.
Wendy

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{{ Dr. Gilbert discusses reports that Parkinson’s disease has a unique odor detectable by trained dogs and rare people with very sensitive senses of smell. }}

It won’t be long before Medicare Advantage is offering “trained dogs” as a Primary Care option.

intercst

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Along with CAT scans. :wink:
Wendy

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Although many fats and oils are difficult to analyze by GC, their fatty acids are often measured as methyl esters. This gives a characteristic finger print rather than the true analysis of the many scrambled triesters of fatty esters with glycerine.

You wonder if lipids might be analyzed as methyl esters too.

If five fatty acids are present you expect them to be all possible combinations of abcde. Aaa aab aba baa bba bab . . . eee. A real mess to analyze. And each with potentially its own properties and medical effects. Much to be studied.

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@pauleckler it’s worth reading the original articles which I linked. The different groups were finding a mixture of ketones, aldehydes, carboxylic acids, hydrocarbons and esters which provided a fingerprint that was characteristic of illness. These weren’t triesters but VOCs of relatively low MW.

image

Wendy

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