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).

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


CR cervical resistivity, AUC Area Under the ROC Curve, LR Likelihood ratio, PPV positive predictive value, NPV negative predictive value, * P < 0.05.

Jokhi et al. BMC Pregnancy and Childbirth 2009 9:40   doi:10.1186/1471-2393-9-40

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