Investigation of Five Algorithms for Selection of the Optimal Region of Interest in Smartphone Photoplethysmography

Table 1

Comparison between heart rates measured by the electrocardiogram and those measured by the smartphone using the five algorithms for selection of region of interest.

Algorithm		SEE (bpm)	Bland-Altman analysis
			Bias (bpm)	LA (bpm)
VAR versus ECG	0.975 ()	2.45		4.80
SER versus ECG	0.913 ()	4.65		9.13
TM versus ECG	0.991 ()	1.49		2.89
TD versus ECG	0.992 ()	1.40		2.72
GRAD versus ECG	0.971 ()	2.51		4.95
FCR versus ECG	0.919 ()	2.26		4.43

Note that two subjects were excluded for the FCR algorithm; namely, the number of subjects was 48 for the FCR algorithm and 50 for the other algorithms. : Pearson correlation coefficients; SEE: standard error of estimate; LA: limit of agreement = 1.96 × standard deviation; VAR: variance; SER: spectral energy ratio; TM: template matching; TD: temporal difference; GRAD: gradient; FCR: fixed central region; bpm: beat per minute.