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Validation Information: Oxford FFQ

Little 1999

The validity of dietary assessment in general practice

Objective: To validate a range of dietary assessment instruments in general practice.

Methods: Using a randomised block design, brief assessment instruments and more complex conventional dietary assessment tools were compared with an accepted “relative” standard-a seven day weighed dietary record. The standard was checked using biomarkers, and by performing test-retest reliability in additional subjects (n=29).

Outcomes: Agreement with weighed record. Percentage agreement with weighed record, rank correlation from scatter plot, rank correlation from Bland-Altman plot. Reliability of the weighed record.

Setting: Practice nurse treatment room in a single suburban general practice.

Subjects: Patients with risk factors for cardiovascular disease (n=61) or age/sex stratified general population group (n=50).

Results: Brief self completion dietary assessment tools based on food groups eaten during a week show reasonable agreement with the relative standard. For % energy from fat and saturated fat, nonstarch polysaccharide, grams of fruit and vegetables and starchy foods consumed the range of agreement with the standard was: median % difference -6% to 12%, rank correlation 0.5 to 0.6. This agreement is of a similar order to the reliability of the weighed record, as good as or better than test standard agreement for more time consuming instruments, and compares favourably with research instruments validated in other settings. Underreporting of energy intake was common (40%) and more likely if subjects were obese (body mass idex (BMI) ≥30 60% under-reported; BMI <30 29%, p<0.001).

Conclusion: Under-reporting of absolute energy intake is common, particularly among obese patients. Simple self assessment tools based on food groups, designed for practice nurse dietary assessment, show acceptable agreement with a standard, and suggest such tools are sufficiently accurate for clinical work, research, and possibly population dietary monitoring.

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Validation Information

Year of Publication

Tool Information

Dietary Exposure Measured
Full Nutrient, Food Groups
Tool Type
Food Frequency Questionnaire
Timeframe Tool Measures info
1 Year
Portion Size Measures info
'Medium servings' or specified units using household measures. 'Medium servings' were derived from experience with other dietary surveys and from published values (Crawley, 1988).
Reporting Method info
Usual; Retrospective
Format info
Supplements Measured
Not Reported
Administration Method info

Study Information

Study Location
Southampton, England
Associated Nutrient Database
Royal Society of Chemistry database
Comparator Validated Against
Weighed Food Diary


Sample Size
Adults, Elderly
Age of Population

Range: 18-80 years

Other Notable Characteristics
Patients in a primary care setting

Total number of nutrients validated: 2 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.

  • Macronutrients: 1
  • Micronutrients: 1
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
Weighed Food Diary Adults, Elderly Both Fibre (NSP) (g) 26% (Median) 0.38 (S)
Vitamin C (mg) 54.6% (Median) 0.56 (S)
Fruit and Vegetables (g) 66.4% (Median) 0.59 (S)

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.

Little P, Barnett J, Margetts B, Kinmonth AL, Gabbay J, Thompson R, Warm D, et al. The validity of dietary assessment in general practice. Journal of Epidemiology and Community Health. 1999 Mar 1;53(3):165-72.