Skip to main content

Table 2 Validity of LMP compared to CRL for gestational age estimation, overall and by parity, rural Bangladesh, 2008–2009

From: A home calendar and recall method of last menstrual period for estimating gestational age in rural Bangladesh: a validation study

 

All

Nulliparous

Parous

Ultrasound visit

(n = 353)

(n = 134)

(n = 219)

Gestational agea

 Last menstrual period, days

76.1 (12.5)

78.8 (12.8)

74.4 (12.1)

 Crown-rump length, days

73.3 (12.9)

74.6 (12.7)

72.5 (13.0)

 LMP-CRL, days

2.8 (10.8)

4.2 (10.0)

1.9 (11.2)

Convergent validityb

 Pearson’s correlation coefficient

0.63

0.69

0.61

 Bias Correction Factor

0.98

0.95

0.99

 Lin’s concordance correlation coefficient (95 % CI)

0.63 (0.56, 0.69)

0.66 (0.56, 0.75)

0.60 (0.52, 0.68)

Live birth

(n = 332)

(n = 127)

(n = 205)

Gestational agea

 Last menstrual period, days

276.2 (18.1)

275.9 (17.7)

276.5 (18.4)

 Crown-rump length, days

273.4 (14.2)

271.6 (13.6)

274.6 (14.5)

 LMP-CRL, days

2.8 (10.7)

4.3 (10.0)

1.9 (11.0)

Convergent validityb

 Pearson’s correlation coefficient

0.81

0.83

0.80

 Bias correction factor

0.96

0.93

0.97

 Lin’s concordance correlation coefficient (95 % CI)

0.77 (0.73, 0.81)

0.77 (0.71, 0.83)

0.77 (0.72, 0.83)

Validity of classifying preterm

 Prevalence of preterm by LMP, % (n)

10.8 (36)

13.4 (17)

9.3 (19)

 Prevalence of preterm by CRL, % (n)

8.7 (29)

11.0 (14)

7.3 (15)

 Sensitivity, %

86.2

92.9

80.0

 Specificity, %

96.4

96.5

96.3

 Positive predictive value, %

69.4

76.5

63.1

 Kappa

0.74

0.82

0.68

Validity of classifying post-term

 Prevalence of post-term by LMP, % (n)

14.2 (47)

15.0 (19)

13.7 (28)

 Prevalence of post-term by CRL, % (n)

3.6 (12)

1.6 (2)

4.9 (10)

 Sensitivity, %

66.7

87.2

60.0

 Specificity, %

88.8

87.4

89.7

 Positive predictive value, %

18.2

11.1

23.1

 Kappa

0.24

0.18

0.28

  1. Preterm is <259 days, term is 259-293 days, and post-term is >293 days gestational age by ultrasound; the Hadlock equation is used for CRL estimate of gestational age
  2. LMP first day of the last menstrual period, CRL crown-rump length
  3. aData presented as mean (SD)
  4. bIn validation analysis: Pearson’s coefficient is a measure of precision; the bias correction factor is a measure of accuracy; and Lin’s concordance correlation coefficient is a measure of reproducibility (accounting for precision and accuracy in the same estimate). Perfect correlation/concordance for each measure = 1