Table 2. The capability of different Pi cutoff values to distinguish labor pain in parturients.

Cutoff	Sensitivity	Specificity	Youden index
15.00	0.825	0.633	0.458
16.08	0.783	0.700	0.483
16.99	0.775	0.742	0.517
18.37	0.767	0.833	0.600
19.31	0.717	0.850	0.567
20.11	0.708	0.867	0.575
21.07	0.683	0.875	0.558
22.01	0.650	0.917	0.567

Notes.

The Youden index was calculated and defined as the value of “sensitivity + specificity-1”. The optimal cut-off value was calculated, maximizing the Youden index.