PHOENIX, AZ — Depending on some smartphone apps for accurate blood-pressure readings might not be so smart, suggests new research[1].

The small study evaluated the Instant Blood Pressure app (AuraLife), which was used by 85 adults—over half of whom had hypertension. Once downloaded, the app asked participants to hold their smartphones up to their chest while placing an index finger in front of the device's camera. However, it then "underestimated higher BPs and overestimated lower BPs," report the investigators, led by Dr Timothy B Plante (Johns Hopkins University School of Medicine, Baltimore, MD).

The study hypothesis was that the absolute mean difference would be less than 5.0 mm Hg between the app and standard BP devices. However, the mean differences were actually 12.4 mm Hg for systolic measurements and 10.1 mm Hg for diastolic readings.

In addition, the sensitivity for hypertensive measurements was a low 0.22, which means that "four-fifths of individuals with hypertensive BP levels will be falsely reassured that their BP is in the nonhypertensive range," write the investigators, calling Instant Blood Pressure "an unregulated" mobile health (mHealth) app.

The findings were presented at the American Heart Association Epidemiology and Prevention-Lifestyle (EPI|Lifestyle) 2016 Scientific Sessions and simultaneously published online March 2, 2016 in JAMA Internal Medicine.

Regulation Needed for Safety, Standards

In the study, 85 volunteers at least 18 years of age (52% women; mean age 56.6 years; mean body-mass index 27.8 kg/m2) were enrolled at five local centers between August and September 2015. A total of 53% had hypertension, and 91% of these individuals were taking related medications. None of the participants had an arrhythmia or internal device as baseline.

BP measurements were taken in random order using the Instant Blood Pressure app, version 1.2.3 on iPhones and using a standard Omron-907 BP device with cuffs after five minutes of quiet sitting by the participants.

Differences were highly significant between the app and the Omron for readings of both systolic (P<0.001) and diastolic BP (P<0.001).

In fact, the systolic readings "were within 5, 10, and 15 mm Hg of the standard BP measurements 24%, 44%, and 59% of the time, respectively," report the investigators. The diastolic readings were within these numbers 26%, 48%, and 70% of the time, "correlating with the lowest possible accuracy grade in all categories by British Hypertensive Society scoring."

The specificity for hypertensive measurements, which was defined as 140 mm Hg or higher systolic and 90 mm Hg or higher diastolic BP, was 0.92.

Overall, the app's measurements "were highly inaccurate," write the investigators, noting that more than 148,000 copies of the app, available for $4.99, had been sold at time of study.

Although this version of the app is no longer available, the researchers urge clinicians to inform consumers who already have it or who are considering other BP-measuring apps about the findings and to tell them not to adjust therapy based on these types of measurements.

"From a public-health perspective, our study supports partnership of app developers, distributors, and regulatory bodies to set and follow standards for safe, validated mHealth technologies."

"Not a Medical Device"

In a response posted on the company's website[2], AuraLife writes that its app was designed to work only within a range of 102 to 158 systolic BP and 65 to 99 diastolic—and can't generate a reading outside that range, which has been published in both the app and iOS App store.

"Approximately 20% or one out of every five of all comparative measures made by Plante et al were for reference pressures outside of the . . . supported range [and] were associated with misuse of Instant Blood Pressure," they write in their statement.

They also note that their "server-side algorithm" for the app was updated at least five times during the study period, which wasn't taken into account by the investigators, and that the app is not a medical device—and therefore shouldn't have been compared with a standard, cuff-using BP device.

However, "We share the authors' concern at the idea of individuals, against the will of their physician, titrating their own therapies."

The study was funded by a PJ Schafer cardiovascular research grant and by an Institutional National Research Service Award National Institutes of Health training grant. Plante reports no relevant financial relationships. Disclosures for the coauthors are listed in the article.

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