The reference device used in the study was the Omron M3 IntelliSense (Omron Healthcare, Inc, Kyoto, Japan), which was validated according to the ESH-IP2 [22]. It consists of an automatic oscillometric sphygmomanometer for the automatic measurement of BP and HR at the arm. The device has 2 available sleeve sizes: a standard size that fits arm circumferences of 22 to 32 cm and a larger size for arm circumferences of 32 to 42 cm.

The device to be validated was the iHealth Track automatic device (KN-550BT; iHealthLabs Europe, Paris, France), which records brachial BP with the oscillometric method, with a range of pressure of 0 to 300 mm Hg (measuring accuracy ±3 mm Hg) and an HR range of 40 to 180 beats/min (measurement accuracy ±5%).

The systolic BP (SBP), diastolic BP (DBP), and HR are displayed on a liquid crystal display screen. The device has enough memory for 99 measurements. In addition, this unit can be used with Apple Bluetooth 4.0 devices and certain Android Bluetooth 4.0 mobile phones, by means of an app called Health MyVitals, which means that it allows for storage of BP and HR data in wireless devices connected to an iHealth Track and tracks data graphically and visually.

The unit weighs approximately 348 g (batteries and sleeve included). It required 4 AAA batteries with an approximate capacity of 250 measurements. The included standard cuff fits the circumferences of the arm in a range of 22 to 42 cm.

We screened a total of 33 participants. There were 13 men and 20 women. Table 1 shows their age, weight, height, BMI, and arm circumference, as well as the comparison of these according to sex.

Figure 1 shows the validation results for the iHealth Track BP device according to ESH-IP2. The table shows the numbers of measurements differing from the standard device, Omron M3, by 5, 10, and 15 mm Hg or less, for SBP and DBP, according to ESH-IP2 [19]. The mean differences between the standard device and the tested device were 4.19 (SD 4.48) mm Hg for SBP and 3.74 (SD 4.55) mm Hg for DBP.

These analyses showed an absolute difference within 5 mm Hg in 75 of 99 pairs of differences for SBP and in 78 of 99 pairs for DBP (vs at least 73 for SBP and 65 for DBP following ESH-IP2 requirements). We observed an absolute difference within 10 mm Hg in 93 of 99 comparisons for SBP and in 89 of 99 comparisons for DBP (vs at least 87 for SBP and 81 for DBP following ESH-IP2 requirements). Additionally, 94 of 99 comparisons exhibited an absolute difference within 15 mm Hg for SBP an DBP (vs at least 96 for SBP and 93 for DBP following ESH-IP2 requirements). Therefore, we successfully completed part 1 of the device validation for BP.

For part 2 of ESH-IP2, 29 of 33 individuals had a minimum of 2 of 3 comparisons within a 5-mm Hg difference for SBP, and 26 of 33 participants met this requirement for DBP (vs at least 24 of 33 participants for SBP and DBP following ESH-IP2 requirements). On the other hand, 3 comparisons exceeded the 5 mm Hg requirement for SBP and DBP in 3 of 33 participants (vs a maximum of 3 participants for SBP and DBP following ESH-IP2 requirements). Because these 2 conditions were validated, we successfully completed part 2 of the device validation for BP.

Thus, part 3 of the iHealth Track device validation also was passed, because parts 1 and 2 were both validated for SBP and DBP.

Figure 2 shows the validation results for the iHealth Track HR device according to ESH-IP2. The numbers of measurements differing from the standard Omron M3 device by 3, 5, and 8 beats/min or less are reported for HR. The mean difference between the standard and the tested device was 1.95 (SD 3.27) beats/min.

These analyses showed that 89 of 99 comparisons had an absolute difference within 3 beats/min, 91 of 99 comparisons had an absolute difference within 5 beats/min, and 93 of 99 differences had an absolute difference within 8 beats/min. Therefore, we successfully completed part 1 of the device validation for HR.

For part 2 of ESH-IP2, 30 of 33 individuals had a minimum of 2 of 3 comparisons within a 3-beats/min difference for HR. On the other hand, none of the 33 participants had 3 differences exceeding 3 beats/min. Because these 2 conditions were validated, we successfully completed part 2 of the device validation for HR.

Thus, part 3 of the iHealth Track device validation was passed, because parts 1 and 2 were both validated for HR.

With these results, the iHealth Track device meets ESH-IP2 validation criteria for both BP (SBP and DBP) and HR for use in the general population.

These results coincide with the Bland-Altman plots showing the differences in measurements between the iHealth Track device and the Omron M3 for SBP (Figure 3), DBP (Figure 4), and HR (Figure 5).

The results obtained from this research are important because they are the first to show that the iHealth Track device successfully passed both parts of the validation process according to the ESH-IP2 review in the general population [19]. However, these results cannot be extrapolated to other specific populations, such as older, diabetic, or pregnant individuals, because we have not addressed these conditions.

Regarding the validation protocols, the presence of several protocols for this function [16-19] is problematic for several reasons. Manufacturers cannot perform the 3 protocols and experts focus on their own protocols (eg, the AAMI is followed more in the United States and the ESH is followed in Europe), and it is impossible to compare several validation studies that are governed by different principles [23].

In this study, we used the ESH protocol, first published in 2002 [18] and revised in 2010 [19], which has many advantages over previous ones [16,17], but also has some limitations.

First, ESH-IP2 does not specify the number of validation studies needed to validate the instrument, although a few findings suggest that a device should be validated in no fewer than 2 different centers separately [22-24]. In this regard, the protocol of the AAMI recommends conducting more than 1 study but does not specify the number of studies or devices [16]. Therefore, it is important to check the validity of BP measurement devices before widespread application in clinics and homes.

Second, the specific conditions required for the participants recruited in the study exclude children and young people, thus omitting data on the hypertensive population between 18 and 25 years of age.

Third, although we calculated the sample size, consecutive sampling bias should be considered, and a simple randomization sampling process could be more adequate for future studies.

Fourth, ESH-IP2 mentions no explicit criteria for a validation process in specific populations, and we highly recommended that this be taken into consideration in its next revision.

Fifth, although sphygmomanometers measure SBP, DBP, and HR, no version of the international protocol of the ESH considers validating HR. Hence, we have added such a validation based on the protocol criteria in BP and establishing, in this case, the required differences based on the scale of values found after HR measurements, being even more demanding than the ESH.

The results of this study are relevant because they show that an automatic wireless device that measures BP and HR and that can also be linked to new technologies meets the requirements of ESH-IP2.

We highly recommended that the accuracy of iHealth Track be assessed in other specific populations, such as pregnant women, older people, patients with arrhythmia, and so on, using other types of sampling. Also, it would be convenient to extend the validation equipment in order to reduce intraobserver error.