Well, technically, the doctors don't actually do the sniffing. That part is handled by a new class of breath-testing devices that can detect chemical compounds associated with a wide range of conditions. Researchers have discovered that everything from inflammatory bowel conditions and heart disease to lung cancer and asthma have unique "breath signatures" that breath sensors can potentially identify. And, these tests are almost as accurate as traditional blood tests and biopsies.
How does the process work? Decades of research has shown that your breath contains not only what's in your lungs (or in your immediate vicinity), but also clues as to what's in your blood. In the same way that Breathalyzers can calculate your blood alcohol level with relative precision, these new tools can pick up the breath signatures of a variety of illnesses.
While some disorders don't have recognizable compounds (or they just haven't been discovered yet), researchers are hopeful about this "next frontier" in medical analysis. Manufacturers certainly have their work cut out for them, as portable and easy-to-use breath testing equipment is yet to be produced. Still, the thought of a future with fewer needle pricks is definitely an exciting one. (The Atlantic)