Table 2.
Test–retest reliability of a food-frequency questionnaire for adolescents
| FFQ1 | FFQ2 | |||||||
|---|---|---|---|---|---|---|---|---|
| Median | (P25, P75) | Median | (P25, P75) | Spearman r | p | CC% | GM% | |
| Energy (MJ) | 7.1 | (5.3, 8.9) | 6.2 | (4.5, 7.9) | 0.604 | <0.001 | 45 | 5 |
| Protein, g | 75.0 | (50.8, 95.0) | 64.6 | (43.1, 80.9) | 0.624 | <0.001 | 34 | 10 |
| Total fat, g | 54.8 | (44.6, 69.6) | 46.8 | (37.8, 63.8) | 0.573 | <0.001 | 43 | 14 |
| Saturated fat, g | 25.2 | (18.8, 31.8) | 21.9 | (17.1, 30.1) | 0.594 | <0.001 | 48 | 14 |
| Monounsaturated fat, g | 17.1 | (14.1, 21.6) | 15.2 | (12.0, 20.1) | 0.553 | <0.001 | 47 | 14 |
| Polyunsaturated fat, g | 7.0 | (5.9, 9.3) | 6.3 | (4.8, 8.6) | 0.551 | <0.001 | 59 | 16 |
| Trans-fat, g | 1.7 | (1.1, 2.3) | 1.6 | (1.2, 2.2) | 0.480 | <0.001 | 41 | 17 |
| Cholesterol, mg | 198 | (145, 267) | 182 | (136, 233) | 0.680 | <0.001 | 50 | 10 |
| Carbohydrate, g | 221 | (171, 273) | 187 | (137, 245) | 0.605 | <0.001 | 40 | 10 |
| Fiber, g | 16.4 | (12.7, 22.7) | 15.9 | (11.4, 19.0) | 0.478 | <0.001 | 43 | 19 |
| Sugar, g | 47.3 | (23.44, 71.0) | 44.8 | (28.0, 62.7) | 0.660 | <0.001 | 47 | 16 |
| Retinol, mg | 424 | (250, 787) | 431 | (290, 750) | 0.504 | <0.001 | 50 | 10 |
| Vitamin D, µg | 2.2 | (1.4, 3,9) | 2.2 | (1.2, 3.8) | 0.590 | <0.001 | 52 | 16 |
| Vitamin E, mg | 4.9 | (4.2, 6.3) | 4.8 | (3.6, 5.9) | 0.638 | <0.001 | 52 | 16 |
| Thiamin, mg | 1.1 | (0.8, 1,5) | 1.0 | (0.7, 1.4) | 0.571 | <0.001 | 50 | 12 |
| Riboflavine, mg | 1.9 | (1.2, 2.5) | 1.5 | (0.9, 2.3) | 0.605 | <0.001 | 47 | 16 |
| Vitamin C, mg | 79 | (50, 120) | 66 | (50, 105) | 0.663 | <0.001 | 43 | 9 |
| Calcium, mg | 1,012 | (594, 1,291) | 814 | (439, 1, 152) | 0.589 | <0.001 | 53 | 14 |
| Iron, mg | 7.5 | (5.7, 9.9) | 6.8 | (4.8, 8.7) | 0.533 | <0.001 | 34 | 19 |
| Percentage energy intake (E%) | ||||||||
| Protein, E% | 17.7 | 16.0, 19.3 | 17.2 | 15.7, 18.6 | 0.674 | <0.001 | 33 | 10 |
| Fat, E% | 30.3 | 27.2, 32.8 | 31.3 | 26.8, 33.9 | 0.422 | 0.001 | 43 | 19 |
| Saturated fat, E% | 13.4 | 12.2, 14.5 | 11.9 | 6.5, 14.8 | 0.328 | 0.012 | 26 | 22 |
| Monounsaturated fat, E% | 9.3 | 8.3, 10.0 | 8.3 | 6.7, 10.3 | 0.375 | 0.004 | 33 | 22 |
| Polyunsaturated fat, E% | 4.0 | 3.4, 4.6 | 3.9 | 2.9, 4.5 | 0.549 | <0.001 | 40 | 12 |
| Trans-fat, E% | 0.8 | 0.7, 1.1 | 0.8 | 0.6, 1.2 | 0.280 | 0.033 | 29 | 24 |
| Carbohydrate, E% | 52.7 | 49.3, 55.3 | 51.2 | 48.6, 56.1 | 0.531 | <0.001 | 38 | 19 |
| Sugar, E% | 12.0 | 7.7, 16.0 | 11.4 | 8.8, 17.1 | 0.638 | <0.001 | 48 | 10 |
Median, 25th and 75th percentile, Spearman correlation coefficient, percent correctly classified (CC) and grossly misclassified (GM) into quartiles of nutrient intake (n=58).