In "Jeopardy!" Watson was asked for one correct answer, whether it was answering questions about Sir Christopher Wren, the Lion of Nimrud or the Church Lady from "Saturday Night Live."
But in its medical guise, when presented a set of symptoms, Watson offers several possible diagnoses, ranked in order of its confidence.
"In medicine, we don't want one answer, we want a list of options," Chase said.
Kesselman said having options might help doctors accept a computer's findings.
"Will a physician ever blindly accept a diagnosis coming out of a computer? I don't think that will happen anytime soon," he said.
Chase said seeing more than one choice might also help doctors move away from what he called "anchoring," or getting too attached to a diagnosis.
"If a person has a 95 percent chance of having disease X, there's still a one-in-20 chance that they have something else," he said. "We often forget what's in that 5 percent. But Watson won't."
The treatment application works much like the diagnosis application. In the demonstration, Watson first suggested the antibiotic doxycycline for treating Lyme disease, then switched to cefuroxime when told the patient was pregnant and allergic to penicillin.
Chase said Watson will know the latest treatment guidelines — which are complex and often updated — "and can see if they're not being met."
"You have to match the right treatment with each unique patient," Chase said. "You can't treat everybody with high blood pressure the same way — a 75-year-old man with prostate cancer who felt dizzy last week and a 32-year-old woman."
Yuan said Watson's influence will depend on "how widely it is adopted."
"You have to wonder if a hospital is going to plunk down a couple of million dollars," he said.
IBM's Dan Pelino, general manager for global health care, said clients won't have to buy a complete Watson system. He said possible future uses include:
— Allowing a doctor to connect to Watson's database by speaking into a hand-held device, using speech-recognition technology and cloud computing;
— Serving as a repository for the most advanced research in cancer or other fields;
— Providing an always-available second opinion.
"You can imagine someone asking Watson a question on an iPad as they're walking down the hall," Chase said. "It might get updates like a GPS."
An existing private medical database known as Isabel is already used by some multi-hospital health systems. Co-founder Jason Maude of Isabel Healthcare said that from what he's heard about IBM's plans for Watson, "It's kind of what we've had for about 10 years."
An online demonstration of Isabel showed similarities to the Watson model — symptoms are entered, and the computer searches through a database for a possible diagnosis. Maude, who named Isabel for a daughter who escaped a serious misdiagnosis as a child, says Isabel's database has been "tuned and honed" over time.
He said prices for using Isabel range from a few thousand dollars a year for a family practice to as much as $400,000 for a health system.
Pelino said Watson is much faster and Chase said Watson is better at understanding non-medical terms.
"Watson knows that 'difficulty swallowing' is 'dysphagia,'" he said.
Isabel has been used at the Orlando Health hospital network in Florida since last fall, and "has had its successes," said Dr. Jay Falk, chief academic medical officer. He said less experienced doctors use it under the guidance of senior clinicians "who can make some judgments about the likelihood of what's given on the list of diagnoses."
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