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Table 5 Prediction of labour duration ≥ 24 hrs -- Bishop score vs. cervical resistivity with 12 mm probe (data shown for 4 frequencies 9.8-78.1 kHz).

From: The role of cervical Electrical Impedance Spectroscopy in the prediction of the course and outcome of induced labour

  Correlation coefficient AUC (95% CI) Optimal cut-off value Sensitivity % (95% CI) Specificity % (95% CI) +LR -LR PPV (%) NPV (%)
Bishop score -0.05 0.54 (0.47 - 0.61) ≤ 3 34.6 (17 - 56) 86.0 (80 - 91) 2.46 0.76 27 90
Frequency of CR          
9.8 kHz 0.09 0.60 (0.53-0.67) >1.93 Ω.m 92 (70.8 - 98.6) 29 (24.6 - 38.9) 1.33 0.29 15.3 96.2
19.5 kHz 0.14* 0.65 (0.58-0.72)* >2.30 Ω.m 58.3 (37.0 -- 78.0) 66 (58.0 -- 73.0) 1.70 0.63 19.0 92.0
39.1 kHz 0.16* 0.66 (0.59 --0.73)* >2.25 Ω.m 75.00 (49.8 - 89.2) 56.00 (48.3 - 63.5) 1.70 0.45 19.0 94.2
78.1 kHz 0.16* 0.65 (0.58-0.72)* >2.27 Ω.m 70.8 (45.1 - 86.1) 58.9(52.3 - 67.3) 1.72 0.50 19.1 93.6
  1. CR cervical resistivity, AUC Area Under the ROC Curve, LR Likelihood ratio, PPV positive predictive value, NPV negative predictive value, * P < 0.05.