ROC analysis
The receiver operating curve analysis revealed that the QTa/RR slope of 0.211 at the entire 24-hour Holter was the best cutoff value for differential diagnosis between LQT1 and LQT2 (sensitivity: 80.0%, specificity: 75.0% and area under the curve: 0.804 [95%CI = 0.68-0.93], Figure 6 ). Meanwhile, it showed an optimal cutoff point of 0.255 of the QTe/RR slope with 60.0% sensitivity and 89.3% specificity. The area under the curve of 0.774 (95% confidence interval, 0.64-0.91) was lower than that of the QTa-RR slope.