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Validation Information: FFQ (Prospective cohort study on diet and cancer)
Validation of a dietary questionnaire used in a large scale prospective cohort study on diet and cancer
OBJECTIVE The study was conducted to assess the validity of a self-administered 150-item food frequency questionnaire FFQ, used in a cohort study on diet and cancer 120,852 men and women, aged 55-69. DESIGN SUBJECTS The study was carried out in a subgroup of the cohort 59 men and 50 women 2 years after the baseline FFQ was completed. A dietary record, kept over three 3-day periods, 4-5 months apart, served as reference method. To evaluate the representativeness of the study population for the entire cohort, a comparison was made with the baseline questionnaire of a random sample of the cohort. RESULTS Pearson correlation coefficients between nutrient intakes assessed by the record and the FFQ that was completed afterwards ranged from 0.40 95 CI 0.22-0.54 for vitamin B1 to 0.86 95 CI 0.80-0.90 for alcohol intake, with correlations for most nutrients between 0.6 and 0.8. Adjustment for energy intake and sex did not materially affect these correlations, except the correlation for fat intake, which changed from 0.72 to 0.52. Correlation coefficients were only slightly modified when the results were extrapolated to the cohort at large. Correction of correlation coefficients for attenuation by day-to-day variance in the record data improved them by 0.07 on average. CONCLUSIONS It is concluded that the FFQ is able to rank subjects according to intake of food groups and nutrients. Despite a better performance of validation study participants, this conclusion also applies to the cohort at large
Total number of nutrients validated: 18
Not all of the nutrients validated in the validation studies are included in the table below, as statistical data was only selected to be displayed for a number of nutrients, this included:
- Saturated Fat
- Mono-unsaturated Fat
- Poly-unsaturated Fat
- Non‐starch polysaccharides(NSP)
- Folic Acid
- Vitamin B12
- Vitamin C
- Fruit & Vegetables
- Urinary Nitrogen
To find information on the other validated nutrients please read the validation study.
- Macronutrients: 8
- Micronutrients: 10
|Comparator||Lifestage||Sex||Nutrient Measured||Mean Difference||Standard Deviation||Correlation Coefficient||Cohen's Kappa Coefficient||Percentage Agreement||Percentage Agreement Categories||Lower Limits of Agreement||Upper Limits of Agreement|
|Estimated Food Diary||Adults||Both||Energy (kcal)||-428.5||1383.6||0.74 (P)||5|
|Protein (g)||-8.9||12.9||0.61 (P)||5|
|Total fat (g)||17.7||20.1||0.72 (P)||5|
|Saturated fat (g)||-9.8||8.7||0.73 (P)||5|
|PUFA (g)||0.8||6.2||0.73 (P)||5|
|Carbohydrates (g)||-26.7||37.5||0.77 (P)||5|
|Fibre (g)||1.6||5.3||0.74 (P)||5|
|Calcium (mg)||-168||274.4||0.60 (P)||5|
|Iron (mg)||-0.4||11.6||0.58 (P)||5|
|Vitamin A (mq eq)||0.08||0.3||0.52 (P)||5|
|Vitamin C (mg)||7.7||37.6||0.58 (P)||5|
|Fruits (g)||-18||89.7||0.60 (S)||5|
|Vegetables (g)||29||115.6||0.38 (S)||5|
Some results have been calculated using statistical techniques based on the published data.
For further information on statistical terms click on Statistical tests used in validation studies
All correlations coefficients in the table are unadjusted unless stated otherwise. For adjusted correlation coefficients and other statistical methods used in the study e.g. paired t-tests, please read the validation articles.
- # Adjusted
- † Energy adjusted.
- ‡ For loge-transformed, energy-adjusted nutrient intakes.
- ^ Adjacent included.
- ᵟ Participants provided identical responses.
- (w) = Weighted.
Goldbohm R.A, Van Den Brandt P.A, Brants H.A.M, Van't Veer P, Sturmans AL.F, & Hermus R.J.J. Validation of a dietary questionnaire used in a large-scale prospective cohort study on diet and cancer. (1994). European Journal of Clinical Nutrition, 48, 253-265.