Table 3.
Intermethod reliability of the BMDCS calcium FFQ to measure calcium intake when compared to the average of three 24-h diet recalls
| Calcium (mg/d) |
Diet Recalls Median (25th, 75th) |
FFQ Median (25th, 75th) |
Difference recalls - FFQ Mean (95% CI) |
Deattenuated Pearson rac | Attenuation factor (λ)bc |
|---|---|---|---|---|---|
| All subjects (n=393) | 871 (652, 1160) | 773 (520, 1145) | 72 (12, 131) | 0.60 | 0.36 |
| Males (n=184) | 924 (741, 1327) | 891 (624, 1269) | 39 (−70, 149) | 0.55 | 0.35 |
| Ages 5–7 y (n=56) | 940 (756, 1112) | 997 (689 1188) | 0 (−100, 100) | 0.74 | 0.37 |
| Ages 10–14 y (n=62) | 1000 (812, 1330) | 917 (669, 1262) | 2 (−133, 138) | 0.54 | 0.29 |
| Ages 15–21 y (n=66) | 845 (656, 1424) | 776 (553, 1352) | 108 (−161, 376) | 0.50 | 0.37 |
| Females (n=209) | 831 (605, 1116) | 650 (458, 993) | 100 (42, 157) | 0.61 | 0.34 |
| Ages 5–7 y (n=57) | 916 (637, 1157) | 821 (542, 1127) | 59 (−26, 145) | 0.69 | 0.50 |
| Ages 10–14 y (n=73) | 874 (671, 1111) | 639 (491, 964) | 126 (20, 232) | 0.54 | 0.27 |
| Ages 15–21 y (n=79) | 743 (538, 1020) | 593 (385, 905) | 105 (3, 207) | 0.61 | 0.30 |
| Black (n=81) | 778 (633, 900) | 706 (478, 925) | 28 (−84, 140) | 0.48 | 0.20 |
| Hispanic (n=68) | 835 (602, 1132) | 700 (467, 1075) | 42 (−99, 183) | 0.54 | 0.26 |
| White (n=194) | 963 (744, 1280) | 872 (557, 1172) | 113 (21, 205) | 0.62 | 0.42 |
Abbreviations: CI, confidence interval; FFQ, food frequency questionnaire; ln, natural log; ro, observed Pearson correlation; BMDCS, Bone Mineral Density in Childhood Study.
Notes: All values for the 24-h diet recall are for the three day average.
a
Deattenuated for random measurement error in the 24-h diet recalls: ro √(1 + [S2w/S2b]/3).
b
λ = slope of the regression of the average of the three 24-h diet recalls on the FFQ.
c
Calculated for the natural log transformed values.