Researchers at Stanford University School of Medicine have launched a clinical study using Apple’s ResearchKit to monitor the daily activity of people with peripheral artery disease (PAD).

The app, VascTrac, will be using data from the participant’s iPhone to measure how far and long they can walk, which is a key indicator of the level of pain they are experiencing from the circulatory condition. People with peripheral artery disease start cramping and feeling pain when they walk or climb stairs because of the plague buildup in their peripheral arteries, usually in the legs. The condition, which affects some 12 million people in the United States, can lead to stroke or heart attack.

“People with peripheral artery disease may be able to walk five miles, but sudden pain may cause them to stop often,” Dr. Oliver Aaalami, clinical associate professor of vascular surgery and lead investigator of the study said in a statement. “These patients can rest and the pain goes away and they move on, often not realizing they could be in trouble.”

Getting daily activity data will help doctors address the “black hole” of time between doctor visits after people with PAD undergo an endovascular procedure such as balloons or stents in the iliac or femoral arteries. While these procedures work for a little while, Aalami said, 60 percent of them fail because patients develop scar tissue. 

“We’re not perfect at predicting who is going to have problems, and catching them early when these stents go down would be the Holy Grail,” said Aalami. “It’s much easier to fix earlier.”

The VascTrac app will ask participants to complete a five to 10-minute initial survey, and quarterly surveys will follow to occasionally measure how far they can walk. To track their activity, all they have to do is keep their iPhone with them during the day – the app uses an algorithm to passively calculate distance. All data will be stored using military-grade encryptions and random codes will stand place of participants’ names. If they agree to it, participants’ anonoymzed data can be shared with other research institutions.

The goal is to enroll 2,000 to 5,000 participants, which is much more than a traditional study. Stanford has reason to expect a good turnout – the institution was one of the first to launch a clinical research study when ResearchKit was first made available last year. The MyHeartCounts study, which incorporated data from 23andMe, has enrolled 54,000 people so far.

Since most patients are only seen at three, six and 12-month intervals after the procedure, having access to data through the app will help doctors develop precision health treatments.

Neil Gandhi, a Stanford medical student and co-investigator of the study said the ResearchKit data could potentially be a “game changer.”

“It could change the way physicians practice,” Gandhi said in a statement. “By using personalized tracking, participants could get a notification to come in for an ultrasound when physicians see signs of claudication. This could ultimately improve care.