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

Table 4 Mean intakes in each quintile based on corresponding serum concentrations and cross-classification between quintiles of intakes and serum concentrations (n = 167)

	Corresponding serum concentrations					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
Intakes
Folate [μg/day]	209 ± 96	258 ± 91	249 ± 91	286 ± 101	296 ± 134	64.7	4.8	0.003
[μg/1,000 kcal]	115 ± 39	145 ± 46	139 ± 49	145 ± 35	164 ± 58	61.1	3.6	0.002
Vitamin B₁₂ [μg/day]	4.62 ± 2.43	6.36 ± 4.20	6.02 ± 2.91	4.88 ± 1.81	6.82 ± 3.17	54.5	4.2	0.029
[μg/1,000 kcal]	2.57 ± 1.29	3.23 ± 1.68	3.20 ± 1.24	2.90 ± 0.84	3.58 ± 1.41	59.9	4.2	0.005

Folate and vitamin B₁₂ intakes were assessed by a self-administered diet history questionnaire (DHQ)
¹Agreement and discordance in quintile ranking was assessed as the percentage classification for the pregnant women based on intake and corresponding serum concentration in the same, adjacent, and opposite quintiles.
²Linear regression analyses were performed to test for significant linear trends between intakes and serum concentrations, adjusting for research settings. The dependent variables were log-transformed

ISSN: 1475-2891