Statistical analyses
PPG values are presented as the mean \(\pm\) standard error of mean
(SEM). The criterion of statistical significance was \(p<0.05\) for
all PPG characteristics. We applied Origin (OriginLab Corp.) for the
ROC-analysis and for the two-way ANOVA at the \(\alpha\)=0.05 to test
for differences between PPG amplitudes and the age and sex of study
subjects. Statistical characteristics including correlation coefficient,
sensitivity, specificity, positive and negative predictive value (PPV
and NPV, respectively), and accuracy were calculated using MATLAB.
RESULTS