There are countless new health related apps for your smartphone coming on the market every month. They can measure your heart rate, help with differential diagnosis and possibly even measure your blood pressure. Researchers at John Hopkins University looked to see how accurate one of the most popular blood pressure measuring apps was. They published their study in the March 2016 issue of JAMA Internal Medicine. First a little background on how popular some of these apps are. The app that they studied was selling about 1000 sales/day at 4.99/purchase and was purchased and downloaded over 148,000 times. The researchers set out to determine if the app was accurate and precise and compared this to the national standard. The study concluded that the blood pressure measurements from the app were highly inaccurate.
The app underestimated higher blood pressures and overestimated lower low blood pressures (See figure) and not just by a little amount
The low sensitivity for hypertensive measurements means that approximately four-fifths (77.5%) of individuals with hypertensive BP levels will be falsely reassured that their BP is in the nonhypertensive range.
Amended excerpt and diagrams from the article:
The app’s systolic BP readings were within 5, 10, and 15 mm Hg of the standard BP measurement 24%, 44%, and 59% of the time, respectively, whereas respective proportions for diastolic BP were 26%, 48%, and 70%, correlating with the lowest possible accuracy grade in all categories by British Hypertensive Society scoring.5 Spearman ρ was 0.44 (P < .001) for systolic BP and 0.41 (P < .001) for diastolic BP. Sensitivity and specificity of [the app] for hypertensive BPs were 0.22 and 0.92, respectively.
This study raises some significant public health issues and begs the questions of whether there should be a formal approval process or greater warnings for these direct to consumer products.