Physicists have developed a simple breath test that may be capable of detecting Type I diabetes.

The results, presented on 5 March at a meeting of the American Physical Society in Denver, Colorado, could lead to non-invasive ways to check for the disease, and possibly even a cheap new tool for monitoring daily glucose levels without drawing blood.

Type I diabetes, often called juvenile diabetes, is a condition in which the body fails to produce insulin, a chemical that breaks down glucose. The resulting elevated blood-sugar levels can send patients into shock, and over the long term can lead to blindness, kidney damage and heart disease. It can also cause a fruity smell on the breath.

Today, Type 1 diabetes is detected by directly extracting a small amount of blood and measuring the amount of glucose it contains. But it may also be possible to detect diabetes on the breath, long before the fruity smell is detectable to the human nose, according to Armstrong Mbi, a graduate student at Mississippi State University.

Mbi and his advisor Chuji Wang have developed a new technique to detect acetone, one of the chemicals whose presence in the lungs increases when blood-sugar levels are elevated.

The team injected acetone-laden water vapour into a small chamber with mirrors on both ends. They then flashed an infrared laser sensitive to the acetone into the chamber. By detecting the amount of time it took the light to completely dissipate as it bounced back and forth between the mirrors, the duo was able to detect trace amounts of acetone down to concentrations of 0.45 parts per million by volume (ppmv).

Mbi says that preliminary tests show that typical diabetics have acetone levels greater than 1.4 ppmv. Based on their new test, he says "we could tell if you're diabetic or not."

No more pin pricks

The new technique sounds potentially useful to Matt Petersen, director of information resources for the American Diabetes Association in Alexandria, Virginia. Current tests are highly accurate but require blood samples. "Non-invasive techniques are always better," he says. If the technique could be extended to test daily blood-sugar levels, then it would be "extremely interesting".

Current tests require diabetics to prick their finger several times a day to test blood-sugar levels. Although only tiny amounts of blood are drawn each time, it is still an invasive procedure.

Researchers have pursued several avenues towards non-invasive tests, including developing a wrist-watch-like device that measures glucose levels in fluid drawn electrically from sweat glands. Such watches can be handy for spotting trends in glucose levels throughout the day, but they are not meant as a replacement for blood tests, and are expensive and prone to errors if the wearer starts to sweat.

Wang says that they plan to test whether they can pick up known diabetics from a breath test. But more will need to be done, he says, to characterize the relationship between acetone on the breath and glucose in the blood. "Right now there is a scientific gap," he says. "But I'm confident it can be done."