Signify Health, a health-tech company that helps monitor patients outside of the hospital, has acquired TAV Health, a start-up that builds cloud-based tools to connect health providers to community health services.

CNBC has learned that the deal was in the high double-digit millions, but the companies declined to comment further on the financial terms. Signify has a multi-billion dollar valuation, the company said.

Signify works on a space that has become an increasingly hot topic for health tech companies — and has drawn the attention of tech giants like Facebook — as medical companies look for new ways to factor in "social determinants" to keep patients healthy after they leave the hospital or doctor's office.

To keep people healthy, sometimes providing great access to doctors, surgeries and tests isn't enough. What also matters is whether a patient has secure housing, fresh produce and a network of caregivers. Otherwise, they could relapse after a surgery or procedure and end up back in the hospital.

The convergence of these health and social factors is often referred to as the "social determinants of health," and it's increasingly a big trend in the investing world.

"Our biggest problem is that there are a ton of social factors that stand in the way of us making an impact," said Signify CEO Kyle Armbrester

Signify tracks how patients with chronic conditions are faring in nursing facilities and in the home on behalf of its health plan customers. Signify does that by sending over a care team to check in on the patient's environment at home, where they look at things like how much food is in the fridge or if the carpet is smooth to prevent accidental trips and falls. With that data, it's building a more robust health record for each patient.

The privately held company was formed in December 2017 after a merger of CenseoHealth and Advance Health, which was managed by the private equity firm New Mountain Capital. It's run by a former executive of electronic medical record company AthenaHealth.

Armbrester said the company is acquiring TAV, which connects community health organizations like Meals on Wheels with health providers, as it looks to focus more deeply on those social factors.

San Antonio, Texas-based TAV Health was founded by Jamo Rubin, a doctor and serial entrepreneur, who said he started the company because in the medical world, "it's so clear to me now that in the hospital environment or clinic environment, what's really going on with patients is hidden from clinicians."

Companies like TAV and Signify Health can afford to take a more active role in monitoring people's health because hospitals and insurers are increasingly looking for ways to avoid expensive health outcomes, including readmissions to the hospital after a procedure. The federal government in the U.S. is increasingly penalizing hospitals for excessive readmissions, in a goal to better link payment to the quality of care.

These companies are also taking advantage of a big trend that involves taking on risk for a patient population, and making money by keeping those people as healthy as possible.

"We see this as an investment in preventative health," said Matthew Holt of New Mountain Capital, which invested in Signify Health. Holt described the goal for Signify as building a longitudinal record of patient health, including their social and environmental factors, which will be securely stored and shared with plans, doctors, caregivers, employers and also the patients themselves.

He described this as the "single most important element that will enable bending of the U.S. health care cost curve."

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