Reproducibility and validity of the Diet Quality Index Revised as assessed by use of a food-frequency questionnaire

Am J Clin Nutr. 2003 Nov;78(5):941-9. doi: 10.1093/ajcn/78.5.941.


Background: The Diet Quality Index Revised (DQI-R) is a dietary assessment instrument based on 10 dietary recommendations reflecting dietary guidelines and policy in the United States.

Objective: The objective of this study was to assess the reproducibility and validity of the DQI-R as measured by use of food-frequency questionnaires (FFQs).

Design: Diet was assessed separately by two FFQs at a 1-y interval and by two 1-wk diet records. DQI-R scores were computed from each method. Venous blood specimens were collected for measurement of dietary biomarkers. Participants (n = 127) were men aged 40-75 y in a validation study of the Health Professionals Follow-up Study.

Results: Mean DQI-R scores were 69.5 for FFQ-1, 67.2 for FFQ-2, and 62.0 for the diet records out of a possible score of 100. The reproducibility correlation for the 2 FFQ scores was 0.72. Correlations between scores for each of the 2 FFQs and diet records were 0.66 (FFQ-1) and 0.72 (FFQ-2). DQI-R scores from FFQ-2 were directly correlated with plasma biochemical measurements of alpha-carotene (r = 0.43, P < 0.0005), beta-carotene (r = 0.35, P < 0.005), lutein (r = 0.31, P <0.005), and alpha-tocopherol (r = 0.25, P < 0.05) and were inversely correlated with plasma total cholesterol (r = -0.22, P < 0.05).

Conclusions: These data indicate reasonable reproducibility and validity of the DQI-R as assessed by an FFQ. Future studies are needed to examine whether this index and other instruments of diet quality can reliably predict disease outcomes.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.
  • Validation Study

MeSH terms

  • Adult
  • Aged
  • Carotenoids / blood
  • Cholesterol / blood
  • Diet Records*
  • Humans
  • Lutein / blood
  • Male
  • Middle Aged
  • Nutrition Assessment*
  • Nutrition Policy
  • Nutritional Physiological Phenomena*
  • Reproducibility of Results
  • Surveys and Questionnaires*
  • alpha-Tocopherol / blood
  • beta Carotene / blood


  • beta Carotene
  • Carotenoids
  • alpha-carotene
  • Cholesterol
  • alpha-Tocopherol
  • Lutein