Employers concerned with rising costs of health care are turning to wellness firms like Castlight Health or Welltok to use big data to predict employee health needs, reported The Wall Street Journal. Health data firms typically gather information from insurers to predict conditions employees might be at risk for. Some firms take prediction one step further, by including data on where employees shop or whether or not they vote in midterm elections.

The companies, including Walmart, that contract with such firms say that they use the data to help employees lead healthier lives and find lower-cost care options. Employees identified as being at risk for certain conditions may receive emails directly from the contracted health data firm with care tips, recommendations to doctors, and alternative treatment options. The Journal noted that employees uncomfortable with this kind of data collection generally can opt out.

Even so, privacy advocates are concerned about health mining data, and Twitter was in an uproar today over a misunderstanding around a pregnancy-predicting product built by Castlight Health. The platform, Castlight Action, uses variables like a woman's age, the number of children she has, whether she has recently stopped filling a birth-control prescription (information obtained through her insurance), and any fertility-related searches she has performed on their health app, to calculate the likelihood that she is pregnant. They then use this information to send the woman opt-out messages about various aspects prenatal care.

But Castlight Action does not, as many on Twitter feared, share this data with employers. Even if employers wanted to see these figures, Castlight's current technology cannot show them. "We'd actually have to build a completely different product to allow employers access to that information," said Alka Tandon, a product lead who worked on Castlight Action. The current product architecture does not grant employers, or even Tandon, access to personal medical information. Instead, it provides benefits managers with information on various segments of their "employee population."

"You have 2,000 people that are considering back surgery, and you have 1,500 that are at risk for diabetes, and you have, you know, 460 that are considering pregnancy," said Tandon. To further protect individuals from accidental identification, any segment with fewer than 40 people is not reported to a benefits team. HR managers then can decide whether or not to launch a campaign through Castlight, which would send information directly to chosen segments.

Although Castlight does not share raw employee data with businesses, ambiguity and unease about the practice broadly persists. The Wall Street Journal noted that employers "generally aren't allowed to know which individuals are flagged by data mining." We reached out to the other companies mentioned in the article — Welltok Inc., Jiff Inc., ActiveHealth Management Inc., and GNS Healthcare Inc. — to clarify whether or not there are instances in which identifying information about flagged individuals is shared with their employer. No one was available for immediate comment.