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Validation Information: FFQ (South India)

Iqbal 2008

Refinement and validation of an FFQ developed to estimate macro- and micronutrient intakes in a south Indian population

Potential error sources in nutrient estimation with the FFQ include inaccurate or biased recall and overestimation or underestimation of intake due to too many or too few items on the FFQ, respectively. Here we report the refinement of an FFQ that overestimated nutrient intake and its validation against multiple 24 h recalls.

Study design

Data on 2527 participants in south India (Trivandrum) were available for the original FFQ (OFFQ) that overestimated nutrient intake (132 food items). After excluding participants with implausible energy intake estimates (<2·72 MJ/d (<650 kcal/d), >15·69 MJ/d (>3750 kcal/d)) we ran stepwise regression analyses with selected nutrients as the outcomes and food intake (servings/d) as predictor variables (n 1867). From these results and expert consultation we refined the FFQ (RFFQ), and validated it by comparing intakes obtained with it and the mean of two 24 h recalls among 100 participants.

Results

The OFFQ overestimated usual daily nutrient intake before and after exclusions [for energy: 13·39 (sd 5·46) MJ (3201 (sd 1305) kcal) and 10·96 (sd 2·65) MJ (2619 (sd 634) kcal), respectively]. In stepwise analyses, fifty-seven food items explained 90 % of the variance in nutrients; we retained thirteen food items because participants consumed them at least twice monthly and twelve food items that local nutritionists recommended. Mean energy intake estimated from the RFFQ (eighty-two food items) was 7·94 (sd 2·05) MJ (1897 (sd 489) kcal). The de-attenuated correlations between mean 24 h recall and RFFQ intakes ranged from 0·25 (vitamin A) to 0·82 (fat).

Conclusion

We refined an FFQ that overestimated nutrient intake by shortening and redesigning, and validated it by comparisons with 24 h dietary recall data.

Web Link

Validation Information

Author
Iqbal
Year of Publication
2008

Tool Information

Dietary Exposure Measured
Full Nutrient
Tool Type
Food Frequency Questionnaire
Timeframe Tool Measures info
4 months
Portion Size Measures info
Participants estimated portion size with the assistance of pictures
Reporting Method info
Usual; Retrospective
Format info
Paper
Supplements Measured
Not reported
Administration Method info
Self-administered

Study Information

Study Location
Trivandrum, South India
Associated Nutrient Database
Indian food composition table. McCance & Widdowson's Composition of Foods used where particular raw food items not available
Comparator Validated Against
24hr Recall

Participants

Sample Size
1867
Lifestage
Adults
Age of Population

Mean (SD): 50.7 (10.1) years

Sex
Both
Other Notable Characteristics
Subjects were part of the PURE (Prospective Urban Rural Epidemiological Study) Cohort

Total number of nutrients validated: 10 info

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:

  • Energy
  • Fat
  • Saturated Fat
  • Mono-unsaturated Fat
  • Poly-unsaturated Fat
  • Carbohydrates
  • Protein
  • Sugar
  • Non‐starch polysaccharides(NSP)
  • Sodium
  • Calcium
  • Iron
  • Zinc
  • Retinol
  • Folate
  • Folic Acid
  • Vitamin B12
  • Vitamin C
  • Fruit & Vegetables
  • Urinary Nitrogen

To find information on the other validated nutrients please read the validation study.

  • Energy
  • Macronutrients: 5
  • Micronutrients: 5
Comparator Lifestage Sex Nutrient Measured info Mean Difference Standard Deviation info Correlation Coefficient info Cohen's Kappa Coefficient Percentage Agreement Percentage Agreement Categories info Lower Limits of Agreement Upper Limits of Agreement
24hr Recall Adults Both Energy (kcal) 531 633 0.45 (ICC)
Energy (kJ) 2220 2900 0.45 (ICC)
Protein (g) 16.2 30 0.46 (ICC)
Fat (g) 35.4 32 0.40 (ICC)
Saturated fat (g) 26.6 22 0.43 (ICC)
Carbohydrate (g) 36.8 104 0.46 (ICC)
Fibre (g) 2.1 12 0.36 (ICC)
Calcium (mg) 479.4 325 0.5 (ICC)
Zinc (mg) 1.2 3 0.37 (ICC)
Vitamin A (µg) 89.9 563 0.43 (ICC)
Folate (µg) 104.7 116 0.39 (ICC)
Vitamin C (µg) 69.5 84 0.26 (ICC)

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.

Iqbal R, Ajayan K, Bharathi A.V, Zhang X, Islam, S, Soman, C. R & Merchant, A. T. Refinement and validation of an FFQ developed to estimate macro- and micronutrient intakes in a south Indian population. Public Health Nutrition. 2008. 12(1) 12-18