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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