Table 4

Prediction of time to onset of labour > 12 hours by the Bishop Score vs. cervical resistivity (CR) measured with a 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

-0.620**

0.85 (0.80-0.90)**

≤ 5

87.9 (77.5 - 94.6)

67.7 (58.8 - 75.9)

2.72

0.18

59.2

91.3

Frequency of CR

9.8 kHz

0.044

0.53 (0.45-0.60)

>1.69 Ω.m

95.2 (86.7 - 99.0)

18.03 (11.7 - 26.0)

1.16

0.26

37.5

88.0

19.5 kHz

0.029

0.52 (0.45-0.59)

>2.29 Ω.m

46.03 (33.4 - 59.1)

64.75 (55.6 - 73.2)

1.31

0.83

40.0

70.0

39.1 kHz

0.033

0.48(0.40-0.55)

>2.15 Ω.m

49.21 (36.4 - 62.1)

61.5 (52.2 - 70.1)

1.28

0.83

39.7

70.1

78.1 kHz

0.013

0.51(0.44-0.59)

>2.53 Ω.m

26.98 (16.6 - 39.7)

81.97 (74.0 - 88.3)

1.50

0.89

43.6

68.5


CR cervical resistivity, AUC Area Under the ROC Curve, LR Likelihood ratio, PPV positive predictive value, NPV negative predictive value, ** P < 0.01

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

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