Even highly rated mobile health apps don’t always deliver value and consumers should rely solely on ratings and rankings to purchase and download an app, say researchers from John Hopkins.

By screening nearly 300 user reviews and comments for a once popular App claiming to effectively monitor blood pressure, Johns Hopkins researchers found that a high “star rating” doesn’t necessarily reflect medical accuracy or value.

Researchers found that even the presence of app disclaimers warning users not to rely on the app for medical monitoring, diagnosis or treatment effectiveness failed to uniformly dissuade people from doing so, or stop healthcare professionals from recommending the app. That app—Instant Blood Pressure—was withdrawn from the market in July 2015.

“People tend to trust user reviews when shopping online and use them to decide which products to purchase, but that doesn’t cut it for medical apps,” says Timothy Plante,, a physician and current assistant professor of medicine in the Larner College of Medicine at the University of Vermont. “There are certain thresholds of accuracy that need to be maintained, and a five-star rating doesn’t replace clinical validation studies and FDA review,” Plante says.

The researchers say that unregulated mobile health app use could give people a false sense of security.

For the new study, the researchers analyzed 261 user ratings and reviews downloaded from the Apple iTunes store before the app was taken off the market.

The average star rating of the latest version of the app was four out of five stars, and 59% of the reviews assigned the app five stars. Commentary praising the accuracy of the app based on anecdotal experience comprised 42% of the reviews and 10% of the reviews mention inaccuracy.

The Instant Blood Pressure app included a disclaimer that the app shouldn’t be used as a medical device and is for “recreational” purposes only. But 24 reviews, or 10%, claimed to use the app for medical purposes, with 11 people using it to manage their high blood pressure treatments, one person using it to manage kidney disease and another person using it to monitor blood pressure after a heart transplant.

“The data showed that disclaimers aren’t a complete solution and consumers will continue to use these devices to manage their healthcare, which could be dangerous if they are substituting the app for medical care with a professional,” says Seth Martin, assistant professor of medicine at the Johns Hopkins University School of Medicine.

Six reviews came from people who claimed to be healthcare professionals including four nurses and one physician. These people gave an average rating of 4.2 stars out of five. 11 reviews came from people who said their healthcare provider—a total of four physicians and seven nurses—approved of the app. Two consumers noted that a nurse and an emergency room physician disapproved of the app, and as a result gave a one-star rating.

“Physicians need to be careful—if you’re saying you personally use an app, people will trust it,” says Plante.

The Instant Blood Pressure app sold for $4.99 on iTunes and was downloaded 140,000 times before it was withdrawn, says John Hopkins. It ranked among the best-selling apps on all of iTunes for much of its stretch on the app store. After the app was withdrawn, the Federal Trade Commission settled with the company for $600,000, with payment suspended for lack of funds in the company,” John Hopkins says.

Many medical apps are still available for consumers, some for over a million downloads.

“We need to actually make sure mobile apps work as intended, in properly designed and conducted clinical studies, before they are relied on for healthcare,” Martin says.

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