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Accuracy of heart rate apps varies
Consumers are being warned about the accuracy of heart rate
apps after a study found huge variability between commercially
available apps, even those using the same technology. The
research is published in the European Journal of Preventive
Cardiology.
1
‘Heart rate apps come installed on many smartphones and
once people see them it is human nature to use them and compare
their results with others’, said last author Dr Christophe Wyss,
a cardiologist at Heart Clinic Zurich, Switzerland. ‘The problem
is that there is no law requiring validation of these apps and
therefore no way for consumers to know if the results are
accurate.’
This study tested the accuracy of four commercially available
heart rate apps (randomly selected) using two phones, the iPhone
4 and iPhone 5. Some apps use contact photoplethysmography
(touching fingertip to the phone’s built-in camera) while other
apps use non-contact photoplethysmography (camera is held in
front of the face).
Accuracy was assessed by comparing the results with
the clinical gold-standard measurements. These are the
electrocardiogram (ECG), which measures the electrical activity
of the heart using leads on the chest, and fingertip pulse
oximetry, which uses photoplethysmography.
The study included 108 patients who had their heart rate
measured by ECG, pulse oximetry, and each app using each
phone.
The researchers found substantial differences in accuracy
between the four apps. In some apps there were differences of
more than 20 beats per minute compared to ECG in over 20%
of the measurements. The non-contact apps performed less well
than the contact apps, particularly at higher heart rates and
lower body temperatures. The non-contact apps had a tendency
to overestimate higher heart rates.
Dr Wyss said: ‘While it’s easy to use the non-contact apps –
you just look at your smartphone camera and it gives your heart
rate – the number it gives is not as accurate as when you have
contact with your smartphone by putting your fingertip on the
camera.’
But the performance of the two contact apps was also
different. One app measured heart rate with comparable accuracy
to pulse oximetry but the other app did not give the correct
measurement. ‘The one contact app was excellent, performing
almost like a medically approved pulse oximeter device, but
the other app was not accurate even though they use the same
technology’, said Dr Wyss.
The researchers tried to find the reason for the difference
in performance between the two contact apps, but they found
that the variation could not be explained by camera technology
(iPhone 4 versus iPhone 5), age, body temperature, or heart rate
itself.
‘The difference in performance between the contact apps is
probably down to the algorithm the app uses to calculate heart
rate, which is commercially confidential’, said Dr Wyss. ‘It means
that just because the underlying technology works in one app
doesn’t mean it works in another one and we can’t assume that
all contact heart rate apps are accurate.’
Dr Wyss said: ‘Before you measure your heart rate, have
a specific question in mind, don’t just measure it for fun. For
example, “is my heart rate too high when I feel something
strange in my heart?” or “is it too low when I feel dizzy?”.’
He concluded: ‘Consumers and interpreting physicians need
to be aware that the differences between apps are huge and there
are no criteria to assess them. We also don’t know what happens
to the heart rate data and whether it is stored somewhere, which
could be an issue for data protection.’
1.
CoppettiT,
etal
.Accuracyof smartphoneappsforheartratemeasure-
ment.
Eur J Prevent Cardiol
2017. DOI: 10.1177/2047487317702044.
Source:
European Society of Cardiology Press Office