A potentially watershed moment in the evolution of digital health occurred last week.

Atlanta-based health and wellness social network Sharecare launched AskMD, a mobile, consumer-facing app that includes a symptom checker unlike any other symptom checker out there. As MobiHealthNews reported:

Sharecare's app, AskMD, offers users a symptom checker that allows them to choose which symptoms they are feeling and then see which potential health issues they might have. The app then walks the user through a "consultation" in which the app will ask the user a series of questions to identify more specifically what the symptom feels like, when it started, and if there are any other symptoms accompanying it. After the "consultation," the user can enter in any information about medications that they are taking. When users have finished entering information, AskMD generates a list of potential problems the user might have ordered by the commonality of the potential problems.

What's so special about that, you wonder? The technology to generate the problem list comes from PKC Corp., a Burlington, Vt., company that Sharecare purchased in June 2012 for an undisclosed sum. PKC, which stands for "problem-knowledge couplers," was the brainchild of medical informatics pioneer Dr. Larry Weed, who has been pushing for the computerization of medicine for six decades.

Weed, 90, believes that the human mind simply is not capable of remembering every nuance of medicine when standing in front of a patient. Instead of relying on memory and education, he has long said, physicians should let computers match up medical knowledge to each patient's specific issues.

Despite his age, Weed commanded the stage for nearly 75 minutes during a presentation to a physician informatics symposium at HIMSS13 in March and explained his convictions far more eloquently than I am able to.

"The public thinks that you know all 70-odd causes of chest pains," Weed told fellow physicians during that memorable keynote. "They think we know all 70 causes. They think we know the five or six things about each cause that you should check on a routine history and that you can keep score in your head and say, 'Mrs. Jones, I think you've got such-and-such,'" he explained.

"There's not a doctor in this room who would stand up and say, 'I know all of that,'" Weed continued. "What does that mean? We're all playing with half a deck. … No two doctors ever play with the same part of the deck and no one plays with a full deck."

Knowledge couplers eliminate the need to type out explanations, help physicians document cases and lead to automatic outcomes studies. "You realize when you see something like that, we're in the dark ages about moving information," Weed told the HIMSS audience in between the two standing ovations he received. "Never move it through heads." Instead, let computers do the work, he said.

Weed, creator of the problem-oriented medical record and the now-ubiquitous SOAP (subjective, objective, assessment, plan) note for documenting medical records, may be a forward thinker and a skilled educator. But, like so many other physicians, he hasn't been the best businessperson, so PKC never lived up to its commercial potential prior to the Sharecare acquisition.

Weed started a previous incarnation of PKC in 1982, established the current company in 1991, and left it in 2006, after a falling out with management he brought in. He remained the principal shareholder until the sale to Sharecare, which was started by two proven entrepreneurs, TV host Dr. Mehmet Oz and WebMD founder Jeff Arnold. 

PKC has been in use at U.S. military hospitals for years, but hasn't had a lot of success in the private sector. At the time of the sale a year and a half ago, PKC CEO Howard Pierce told me that his company didn't advertise or even employ a salesperson. Not a single salesperson.

Now, with Sharecare in possession of the PKC technology, AskMD is bringing the power of clinical decision support to the masses. If doctors want to jump on board, great, but if they resist, AskMD could cut them out of the loop.

We're not talking evidence-based medicine, either, but rather personalized diagnostic decision support. EBM is a red herring to Weed because it relies on probabilities, not each patient's specific conditions. "The patient isn't interested in what's probable. They're interested in what's wrong. And if it's highly improbable, they expect you to find it," Weed said at HIMSS this year.

A month before the Sharecare acquisition of PKC, I lost my father to a rare neurodegenerative condition called multiple system atrophy. For three of the five years he fought that fatal ailment, doctors thought he had Parkinson's disease because many of the symptoms are similar. They played the percentages, and they were wrong. So, yeah, probability isn't always the best way to go.

I often frown on direct-to-consumer apps in healthcare, but, as Arnold proved in the early days of WebMD during the dot-com heyday, consumers will turn to automated symptom checkers when they think they're sick. I have no doubt AskMD will find a user base. I also have a feeling at least a few physicians and hospitals will embrace it.

The Sharecare app works by walking consumers through an interview process that captures patient history, branching out to new questions according to each response. With the PKC engine behind it, AskMD essentially helps build a differential diagnosis and management plan – the last two stages of the SOAP note.

This, as Pierce told me in June 2012, lets physicians perform a "targeted physical exam," saving time and hopefully leading to a more accurate medical assessment. The results of the exercise can go into an electronic health record, a patient portal, a personal health record or simply a printout with relevant educational material and follow-up instructions.

By the way, most of those options will help satisfy the patient engagement requirement in Meaningful Use Stage 2. If the app proves interoperable with EHRs and fits patient and clinician workflows, it could be groundbreaking.