Reliability and validity of a smartphone pulse rate application for the assessment of resting and elevated pulse rate

Purpose/hypothesis: This study was designed to investigate the test-retest reliability, concurrent validity, and the standard error of measurement (SEm) of a pulse rate assessment application (Azumio (R)'s Instant Heart Rate) on both Android (R) and iOS (R) (iphone operating system) smartphones as compared to a FT7 Polar (R) Heart Rate monitor. Number of subjects: 111. Materials/methods: Resting (sitting) pulse rate was assessed twice and then the participants were asked to complete a 1-min standing step test and then immediately re-assessed. The smartphone assessors were blinded to their measurements. Results: Test-retest reliability (intraclass correlation coefficient [ICC 2,1] and 95% confidence interval) for the three tools at rest (time 1/time 2): iOS (R) (0.76 [0.67-0.83]); Polar (R) (0.84 [0.78-0.89]); and Android (R) (0.82 [0.75-0.88]). Concurrent validity at rest time 2 (ICC 2,1) with the Polar (R) device: IOS (R) (0.92 [0.88-0.94]) and Android (R) (0.95 [0.92-0.96]). Concurrent validity post-exercise (time 3) (ICC) with the Polar (R) device: iOS (R) (0.90 [0.86-0.93]) and Android (R) (0.94 [0.91-0.96]). The SEm values for the three devices at rest: iOS (R) (5.77 beats per minute [BPM]), Polar (R) (4.56 BPM) and Android (R) (4.96 BPM). Conclusions: The Android (R), iOS (R), and Polar (R) devices showed acceptable test-retest reliability at rest and post-exercise. Both the smartphone platforms demonstrated concurrent validity with the Polar (R) at rest and post-exercise. Clinical relevance: The Azumio (R) Instant Heart Rate application when used by either platform appears to be a reliable and valid tool to assess pulse rate in healthy individuals.