Spit is central to Stephen Swanick's vision for detecting disease.

His product, SaliMark OSCC, which debuted this month, uses genetic material in saliva to judge the risk of whether an oral lesion is cancerous.

Swanick, 51, left his job in the medical-device industry and spent $1.3 million of his own money to pursue this. He founded PeriRx in Broomall in 2008, hoping spit would help spot a spectrum of illnesses, from lung cancer to diabetes.

Instead, it has been a long slog, much like spitting in the wind.

"This is a passion, not a product," Swanick said. "It's been harder than I ever thought."

Salivary diagnosis is enticing, experts say, because it could become an early warning system for cancer and other diseases, and trigger care earlier for patients. But others point out the medical value of spit hasn't been proven, especially in diseases besides cancer. "The jury has not been heard from," said Arnold Baskies, a surgeon in Moorestown.

Oral cancer was diagnosed in about 43,000 Americans last year. It used to afflict mostly smokers and drinkers. But increasingly it shows up in people because of the human papillomavirus, a venereal disease recently linked to oral cancer. Lesions are often not identified as malignant until a late stage, leaving patients a 43 percent of dying within five years, the Oral Cancer Foundation reported.

Care can include disfiguring surgery on patients' jaws and tongue. Many oral lesions are not cancerous, though, and a biopsy is needed to confirm the diagnosis.

Swanick declined to share projections on how big the market could be for SaliMark, but noted that about 25 million people receive biopsies each year, mostly for lesions that turn out not to be cancerous.

The target customers for Sali-Mark are dentists and primary-care physicians, he said.

PeriRx's test, the company's first to reach the market, offers a way to screen patients. The founders, Swanick, dentist Neil Gottehrer, and cardiologist Jack Martin, emphasize the test alone is not designed to definitively diagnose cancer. It assesses risk, and anyone who tests positive should be referred to a specialist, and get a biopsy, if warranted.

Swanick learned about salivary diagnostics from his dentist Gottehrer during a cleaning and began the company to license the salivary diagnostics work of UCLA scientist David Wong, who called noninvasiveness "the holy grail of diagnostics."

Swanick, Gottehrer, Martin, and about 20 other local investors, many friends of the three men, spent $6.5 million to refine Wong's work and create a product, Swanick said.

"Raising money is the most humbling experience that you'll probably get," Swanick said. "We were trying to get people to invest in something that didn't exist."

The company's product identifies three biomarkers in saliva - genes that control cell death, cell repair, and blood-vessel creation - all activities that go into overdrive when cancer is present.

The product would cost patients up to $225 per test, some of which may be covered by insurance, Swanick said. The cost for biopsies varies widely and can exceed the proposed cost of the SaliMark test.

PeriRx's studies on 170 patients with lesions correctly identified squamous cell carcinomas, the most common kind of oral cancer, 96 percent of the time.

"Pretty darn good for a screening tool," said physician Christopher Fundakowski of the Fox Chase Cancer Center, who has no financial stake in the business.

The company's founders noted the test was effective at spotting cancers at an early stage, when there is a more than 93 percent survival rate.

But the test is not widely embraced by cancer experts. Some question the need for it, saying what would be more useful is a test that can identify oral cancers before they form visible lesions.

In trials, the test correctly identified lesions as noncancerous just 58 percent of the time, meaning that a large minority of harmless lesions would test positive for cancer.

Those false positives could cost a lot in time, money, and emotional turmoil, said Kelly Kim, program director at the National Institute of Health's National Cancer Institute. She also noted SaliMark has not won FDA approval, which PeriRx is seeking.

Swanick, who was 18 when his father died of lung cancer, is familiar with the criticisms.

"These DNA, these mRNA, they're in all our bodily fluids," he said. "Why would they not be in your saliva? Has anybody really gone as far as us? Nobody."