Table 6

Mean intakes estimated from the 2nd DHQ across quintiles of intakes estimated from the 1st DHQ (n = 58)

1st DHQ

Agreement (% classified into the same or adjacent quintile)¹

Discordance (% classified into the opposite quintile)¹

Linear trend²

p

1^st quintile

2^nd quintile

3^rd quintile

4^th quintile

5^th quintile

Mean ± SD

Mean ± SD

Mean ± SD

Mean ± SD

Mean ± SD

2nd DHQ

Energy [kcal/day]

1452 ± 498

1786 ± 292

1591 ± 227

1908 ± 300

2120 ± 323

70.7

1.7

< 0.001

Folate [μg/day]³

185 ± 44

241 ± 37

243 ± 60

288 ± 63

447 ± 126

81.1

0

< 0.001

Vitamin B₁₂ [μg/day]³

4.44 ± 2.32

5.03 ± 2.41

5.27 ± 1.51

6.16 ± 1.78

8.77 ± 4.36

77.6

1.7

< 0.001

DHQ: self-administered diet history questionnaire

¹Agreement and discordance in quintile ranking was assessed as the percentage classification for the pregnant women based on the two-time DHQ in the same, adjacent, and opposite quintiles

²Linear regression analyses were performed to test for significant linear trends between estimated intakes from the two-time DHQ

³Linear regression analyses were conducted after log-transformation of the variables

Shiraishi et al. Nutrition Journal 2012 11:15   doi:10.1186/1475-2891-11-15