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Table 3 Test-retest reproducibility of food groups 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

FFQ 2

Spearman’s r

P

CC %

GM %

Kappa k

P

Median

(P25, P75)

Median

(P25, P75)

Milk, yoghurt, milk dessert (ml/day)

184

(103, 335)

168

(54, 266)

0.81

< 0.001

62

0

0.43

0.006

Cheese (g/day)

20

(10, 31)

18

(2.9, 35)

0.82

< 0.001

67

0

0.50

0.001

Eggs (g/day)

18

(16, 54)

18

(12, 66)

0.90

< 0.001

67

0

0.51

< 0.001

Poultry (g/day)

22

(11, 54)

21

(11, 31)

0.76

< 0.001

71

5

0.57

< 0.001

Red meat, non-processed (g/day)

12

(10, 20)

20

(8.5, 28)

0.85

< 0.001

62

0

0.43

0.005

Red meat, processed (g/day)

14

(1.8, 19)

9.3

(1.8, 21)

0.22

0.331

33

14

0.01

0.946

Liver-pate (g/day)

0

(0, 7.1)

2.9

(0, 7.1)

0.69

0.001

71

10

0.54

0.001

Meat dishes (g/day)

45

(23, 66)

45

(21, 67)

0.66

0.001

52

5

0.29

0.063

Fatty fish (g/day)

11

(5.4, 21)

11

(11, 21)

0.40

0.073

71

10

0.56

< 0.001

Lean fish (g/day)

14

(0, 29)

14

(0, 14)

0.79

< 0.001

71

0

0.56

< 0.001

Fish spread (g/day)

7.9

(0, 14)

5.7

(0, 22)

0.70

< 0.001

71

5

0.57

< 0.001

Fish dishes (g/day)

11

(0, 11)

11

(0, 11)

0.46

0.035

43

14

0.23

0.033

Breakfast cereal, high grain (g/day)

14

(7.1, 107)

36

(7.1, 100)

0.83

< 0.001

71

0

0.57

< 0.001

Rice, pasta, noodle (g/day)

76

(46, 113)

76

(43, 133)

0.55

0.010

52

10

0.28

0.066

Bread, crispbread, low fibre (g/day)

5.7

(0, 17)

5.7

(0, 23)

0.75

< 0.001

86

5

0.78

< 0.001

Bread, crispbread, high fibre (g/day)

102

(34, 142)

102

(38, 123)

0.76

< 0.001

71

5

0.57

< 0.001

Nuts, almonds (g/day)

1.4

(0.7, 7.1)

2.9

(0.7, 7.1)

0.64

0.002

71

5

0.56

< 0.001

Potatoes (g/day)

33

(20, 68)

31

(15, 72)

0.76

< 0.001

62

5

0.43

0.006

Vegetables (g/day)

116

(75, 189)

102

(69, 163)

0.84

< 0.001

71

5

0.57

< 0.001

Fruits (g/day)

172

(50, 249)

133

(58, 304)

0.76

< 0.001

67

0

0.50

0.001

Sugar, sweets, desserts(g/day)

28

(12, 37)

25

(12, 39)

0.70

< 0.001

57

5

0.36

0.020

Oils, butter, margarine (g/day)

2.1

(0.4, 16)

2.9

(0, 10)

0.93

< 0.001

81

0

0.71

< 0.001

Coffee, tea, water (ml/day)

964

(789, 1323)

964

(735, 1196)

0.90

< 0.001

76

0

0.64

< 0.001

Juice, sweet drinks (ml/day)

171

(111, 257)

200

(86, 489)

0.72

< 0.001

52

0

0.29

0.060

Alcohol (ml/day)

53

(1.4, 154)

69

(19, 111)

0.83

< 0.001

81

5

0.72

< 0.001

Pizza (g/day)

43

(21, 43)

21

(21, 43)

0.38

0.088

33

5

0.16

0.038

Salty snacks (g/day)

5.7

(2.9, 8.6)

5.7

(2.9, 8.6)

0.58

0.006

48

10

0.21

0.156

Mixed dishes (g/day)

84

(79, 173)

84

(70, 154)

0.75

< 0.001

67

5

0.49

0.001

  1. Food intake (gram/milliliter per day) for food groups (median, 25th and 75th percentile, Spearman’s rank correlation coefficient, percent correctly classified (CC) and grossly misclassified (GM) into tertiles of intake, Cohen’s Kappa value). Statistically significant p-values marked in bold