"Give it the old sniff test" traditionally refers to checking out an idea or proposal.

But one day soon, it may herald a doctor ordering a diagnostic test for diabetes, swine flu and cancer, among other things, according to several research reports.

Scientists in Philadelphia say they have found a way to analyze airborne molecules in the odors given off by human skin cells to detect a specific chemical signature for melanoma, the deadliest type of skin cancer.

A team from the Monell Chemical Senses Center and the University of Pennsylvania said they have developed a sensor device using nanotechnology that allows for non-invasive odor detection of melanoma. Nanotechnology uses engineering and equipment designed to work on a very tiny scale.

The disease, which forms in pigment-producing skin cells called melanocytes, causes three-quarters of all skin cancer deaths, in part because it can spread rapidly to other organs. Early detection is key, but that relies mainly on visual self-exams for moles or spots that seem to be changing quickly and similar checks by a doctor before moving on to biopsy and other tests.

By measuring organic compounds from the cells with a small portable testing device, detection of this type of cancer could come much earlier, with improved odds for survival.

Researchers have already determined that dogs can be trained to identify prostate cancer and melanoma from organic compounds in urine samples and directly from the skin. Breath tests have also been used to detect lung cancer.

The melanoma study results were published online last week by the Journal of Chromatography B.

A second new study, by chemists at the University of Pittsburgh, has shown that diabetics may soon be able to skip blood-glucose tests in favor of a diabetes "breathalyzer" that measures an odor released in the breath. They're one of several groups around the world working on such a device.

Diabetics often notice an odor on their breath from acetone -- a byproduct of an acid produced when the body breaks down fatty acids and doesn't have enough insulin to regulate the process. The fruity or nail polish smell increases significantly with higher blood glucose levels.

The Pitt team was able to develop a new sensor that uses carbon nanotubes and a chemical compound to capture and measure acetone vapors under ultraviolet light. They're now working on additional prototypes that they'll use to test human breath samples directly.

The study was published online June 5 in the Journal of the American Chemical Society.

Researchers at the Cleveland Clinic in Ohio and New Zealand-based Syft Technologies have reported a breath test for swine flu, the H1N1 strain that swept much of the globe four years ago. The test used exhaled nitric oxide -- a molecule linked to viral infections, the flu and viral clearance.

Working with a small group of people vaccinated with a weakened H1N1strain, they found that levels of nitric oxide peaked on the third day after vaccination. The researchers suggest this shows that people infected with this strain of flu trigger their immune response on the third day. So if someone is shown to be infected and already starting to mount natural defenses against this flu by a breath test, it would likely be futile to vaccinate him or her.

The study first appeared in the Journal of Breath Research in 2011. The team first worked on a sensor for nitric oxide to measure asthma, and had also made progress in finding compounds released in the breath of people suffering from liver and kidney disease, heart disease, and pulmonary hypertension.

Contact Scripps health and science writer Lee Bowman at BowmanL@shns.com