Adolescent Populations Methods Validation - NCS Dietary Assessment Literature Review
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- Validation Methods
Table 6.1 presents validation studies on adolescent populations, including the studies included in the comprehensive reviews of the literature through 2000 by McPherson and colleagues (1), and by Livingston and colleagues (161) discussed in Exhibit 5.3.
Food Record (FR) and Diet History (DH) Methods
Food records, either weighed or estimated, and diet histories have received very limited validation in adolescent populations. Energy intake reported on weighed food records underestimated total energy expenditure (TEE) by 18 to 24 percent in two European studies of adolescents (138;196). Likewise, estimated food records underestimated TEE by more than 20%, with obese teens underreporting energy intake by 42% (195). An intensive diet history interview (2 hours) was found to underestimate energy intake by 10 to 14% compared with TEE measurements by the DLW (Doubly Labeled Water) method in both vegans and omnivore adolescents (253;254). Another study found no significant differences at the group level between energy intake reported in a diet history interview and TEE measurements (138). A reanalysis of a 1990 dataset of concurrent measurements of TEE by the DLW method, 7-day weighed food records (FR), and diet history (DH) by Livingston et al. found only 25% of children who underreported energy intake on weighed food records were identified by blanket cut offs of 1.55 x BMR, based on WHO physical activity levels (199). However, only 6 adolescents were included in the dataset. A 3-day weighed FR correlated significantly with biomarkers of folate intake in a population of older (more than 15 years old) Canadian female adolescents (255).
24-Hour Recall (24HR) Interviews
Only two studies have examined the validity of 24-hour recall (24HR) interviews in populations containing adolescents. A comparison between energy intake from three 24HR interviews over a 2-week period and TEE measurements by the DLW method in a large, diverse group of Alabama youth age 9 to 14 years achieved close agreement at the group level, but wide individual variability (200). In this study, data for adolescents were not analyzed separately and study participants were admitted to a metabolic unit for DLW dosing and the first recall. In Minnesota middle school students, a parent-assisted telephone-administered 24HR interview underestimated energy intake reported on a parent-assisted 3-day FR by 12% (256).
Food Frequency Questionnaires (FFQs)
The Youth Adolescent Questionnaire (YAQ), which is an adaptation for adolescents of the Harvard Food Frequency Questionnaire (HFFQ), found close agreement at the group level between energy intake reported on the YAQ and TEE measurements by the DLW method, but not at the individual level (208). Fifty percent of the adolescents misreported intake; misreporting was related to body weight and percent body fat. The YAQ has also been validated with multiple 24HR interviews in mainly white middle-class adolescent populations (188). The 27 fruit and vegetable questions on the questionnaire have been studied in a diverse population (24% black and 15% Hispanic) of high school students; a shorter (6 items) questionnaire had higher correlations with fruit and vegetable intake reported on three 24HR interviews (257).
Small validation studies have assessed a variety of other FFQs in adolescent populations. The differences in the instrument as well as the study designs and adolescent populations limit generalizations of results. In 2002 Van Assema (258) reviewed 26 validation studies of food frequency questionnaires in adults and 8 studies in children/adolescents (167;180;183-185;257;259;260) and concluded available FFQs have only limited capability to make valid assessments of fruit and vegetable intake from children of various socioeconomic status and ethnic groups, although older children and adolescents were generally more accurate than younger children. Larger studies on more diverse groups are needed.
Validation studies on a variety of short questionnaires targeting specific nutrients or food groups are presented in Table 6.1.