Validity and reproducibility of folate and vitamin B12 intakes estimated from a self-administered diet history questionnaire in Japanese pregnant women

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

ISSN: 1475-2891