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Table 2 Relative validity: mean and median intake of food groups, energy and nutrients from FFQ and 3x24HR, percentage difference, and percentage agreement in categories (n = 124)

From: Relative validity of a web-based food frequency questionnaire for Danish adolescents

  FFQ 3x24HR Median diff. % Classification (%)  
Food groups (g/d) Median q1-q3 Median q1-q3   Same quartile Opposite quartile Weighted Kappa
Beverages 1131 648–1273 1032 821–1464 −10 35 9 0.20
Dairy 319 182–636 335 182–521 −4.7 46 6 0.43
Bread 185 109–275 204 146–258 −9 28 7 0.12
Cereals 27 14–50 24 9–52 12 35 6 0.25
Meats/poultry 82* 56–118 107 69–139 −23 23 7 0.05
Fish 11* 6–18 1 0–16 1000 32 18 n.a.
Fruits 126** 52–247 57 9–135 121 43 6 0.32
Vegetables 116* 65–171 91 62–130 27 32 9 0.12
Sweets 17** 10–28 57 24–108 −70 33 4 0.20
Oils & dressing 36* 22–47 26 18–51 38 38 3 0.32
Nutrients Mean or Median SD or q1-q3 Mean or Median SD or q1-q3     
Energy (MJ/d) 7.6 5.7–9.7 8.5 7.0–11.0 −10 36 5 0.26
Protein (E%) 15** 2.7 13 2.5 15 37 6 0.24
Fat (E%) 34* 6.3 35 6.0 −3 34 8 0.24
 SFA (g/d) 26** 19–33 33 23–44 −21 40 2 0.34
 MUFA (g/d) 24* 16–31 27 20–36 −11 45 2 0.39
 PUFA (g/d) 12 8–15 11 9–15 9 36 3 0.29
Carbohydrate (E%) 51 6.5 51 6.0 0 25 14 0.10
Added sugar (g/d) 26** 15–38 41 25–69 −36 31 5 0.23
Dietary fiber (g/d) 21 15–32 18 15–24 16 41 5 0.30
Vitamin C (mg/d) 66** 43–100 49 33–69 34 31 7 0.14
Calcium (mg/d) 867 647–1374 873 672–1229 −0.7 39 6 0.33
Iron (mg/d) 8.3 6.3–12.5 8.3 6.7–10.8 0 40 4 0.29
  1. Variables that reached normality after log-transformation were beverages, dairy, bread, oils & dressing, energy, SFA, MUFA, PUFA, added sugar, dietary fibers, vitamin C, calcium and iron whereas cereals, meat/poultry, fish, fruit, vegetables and sweets did not reach normality after log-transformation
  2. Median difference in percent = median (FFQ-24HR/24HR)*100
  3. FFQ food frequency questionnaire, 24HR, 24-h recalls, SFA saturated fatty acids, MUFA monounsaturated fatty acids, PUFA polyunsaturated fatty acids
  4. *p < 0.05 significantly different from 24HR
  5. **p < 0.001 significantly different from 24HR