Before these heart procedures, surgeons must know whether an artery is healthy enough to snake a catheter through it to the heart to remove any blockages and restore blood flow. Traditionally, they use the so-called Allen test, which involves blocking circulation to the hand until it turns white, then easing pressure on one of two main arteries to see if the hand turns pink again, indicating a healthy artery.

For the study, researchers compared doctors’ assessment of hand color in the Allen test to an experimental circulation measurement app that uses a smartphone camera to monitor changes in color in the fingertips.

With the app, doctors correctly diagnosed artery health 92 percent of the time, compared with 82 percent with the Allen test, researchers report in the Canadian Medical Association Journal.

“Using a smartphone to monitor changes in color in the fingertips is much more accurate in detecting subtle changes as opposed to the doctors’ general opinion of the color of the hand,” said senior study author Dr. Benjamin Hibbert, a researcher at the University of Ottawa Heart Institute in Canada.

While the results suggest that smartphones may one day have potential as medical tools, the app is experimental and not available for widespread use by doctors or patients. Many smartphone apps have not been rigorously tested in clinical trials necessary to win regulatory approval under standards established for medical devices.

Still, the app in the study has the potential to enable doctors to test blood flow at the bedside without buying new equipment and get accurate results that can help surgeons choose which patients may be good candidates for procedures to unblock arteries and restore blood flow to the heart, Hibbert said by email.

One drawback of the study is that it used an older smartphone, the iPhone 4, with software and a camera that’s been changed many times in recent years as new versions of the device have been released. The results might be different with other smartphones, researchers note.

Rapidly evolving smartphone technology makes it hard to test the effectiveness of mobile health tools, and the study was a rigorous evaluation of the technology available at the time that it was conducted, said Dr. Kumanan Wilson, author of an accompanying editorial and a researcher at the University of Ottawa in Ontario, Canada.

“The advantage of the approach outlined in this study is it provides an example of a readily available technology that can be standardized in its application,” Wilson said by email. “Furthermore, the technology was properly evaluated which is often not the case with mobile health technologies.”