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Table 2 Test-retest reproducibility and relative validity of energy and nutrients for the food-frequency questionnaire (n = 21)

From: Reproducibility and relative validity of a newly developed web-based food-frequency questionnaire for assessment of preconception diet

 

FFQ 1

Test-retest reproducibility (FFQ 2)

P

Relative validity (WFR)

P

Median

(P25, P75)

Median

(P25, P75)

Spearman’s r

Median

(P25, P75)

Spearman’s r

Energy (kcal/day)

2310

(1478, 2745)

1921

(1619, 2796)

0.82

< 0.001

2170

(1834, 3042)

0.51

0.018

Energy (kJ/day)

9696

(6194, 11,519)

8086

(6795, 11,722)

0.82

< 0.001

9079

(7672, 12,801)

0.51

0.018

Fat (g/day)

82a

(24)

71

(59, 109)

0.71

< 0.001

93a

(26)

0.37b

0.104

Saturated fat (g/day)

25

(22, 35)

25

(20, 37)

0.77

< 0.001

34

(26, 40)

< 0.05

0.832

Carbohydrates (g/day)

261

(154, 300)

231

(177, 302)

0.86

< 0.001

250

(175, 386)

0.59

0.005

Fibre (g/day)

30

(17, 38)

29

(19, 38)

0.85

< 0.001

33a

(13)

0.70

< 0.001

Protein (g/day)

92

(66, 127)

96

(69, 119)

0.87

< 0.001

98

(71, 110)

0.50

0.021

Alcohol (g/day)

2.8

(0.3, 7.5)

3.8

(1.1, 5.1)

0.83

< 0.001

0

(0, 6.6)

0.71

< 0.001

Vitamin A (RAE/day)

779

(349, 979)

683

(506, 975)

0.87

< 0.001

813

(569, 1356)

0.72

< 0.001

Folate (μg/day)

312a

(135)

298

(199, 416)

0.90

< 0.001

317

(254, 436)

0.78

< 0.001

Vitamin B12 (μg/day)

6.1

(3.7, 8.4)

6.8a

(2.8)

0.86

< 0.001

5.2

(4.3, 6.6)

0.66

0.001

Calcium (mg/day)

811

(623, 1197)

828

(497, 1373)

0.93

< 0.001

1122

(774, 1280)

0.55

0.010

Iron (mg/day)

12a

(4.4)

11a

(4.1)

0.85b

< 0.001

12

(9.8, 17)

0.67

0.001

Iodine (μg/day)

126

(94, 228)

142

(95, 221)

0.88

< 0.001

131

(97, 161)

0.67

0.001

Vitamin D (μg/day)

5.6

(3.3, 7.4)

5.5

(3.3, 7.7)

0.56

0.008

3.9

(2.8, 5.6)

0.46

0.034

Salt (g/day)

7.7

(5.2, 8.9)

6.1

(5.2, 10)

0.85

< 0.001

6.6

(5.6, 9.0)

0.21

0.363

Sugars (g/day)

20

(16, 27)

27

(15, 38)

0.59

0.005

31

(19, 67)

0.62

0.003

  1. Energy and nutrient intake for food-frequency questionnaire 1 (FFQ), food-frequency questionnaire 2 and 7-day weighed food record (WFR). Energy and nutrients presented as median (25th percentile, 75th percentile), Spearman’s rank correlation coefficient and p-value. Vitamin A presented as retinol activity equivalents (RAE = sum retinol + 1/12 beta-carotene). Statistically significant p-values marked in bold
  2. aMean (standard deviation)
  3. bPearson’s correlation coefficient