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Reliability and relative validity of a diet index score for adults derived from a self‐reported short food survey
Author(s) -
Hendrie Gilly A.,
Rebuli Megan A.,
Golley Rebecca K.
Publication year - 2017
Publication title -
nutrition and dietetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.479
H-Index - 31
eISSN - 1747-0080
pISSN - 1446-6368
DOI - 10.1111/1747-0080.12303
Subject(s) - medicine , kappa , reliability (semiconductor) , food group , demography , statistics , food frequency questionnaire , zoology , mathematics , environmental health , biology , power (physics) , physics , geometry , quantum mechanics , sociology
Aim Assess the reliability and relative validity of a diet index score for adults derived using a 38‐item online survey. Methods The short food survey (SFS) measured ‘usual’ intake of seven food groups, three food choice indicators and variety; and was completed by 61 adults aged 19‐50 years from Adelaide, Australia. A score was applied to assess compliance with the 2013 Australian Dietary Guidelines. Reliability of the survey was measured between two administrations one week apart; and validity by comparing the first administration to the average of three 24‐hour dietary recalls. Statistical analyses included paired samples t ‐tests, intra‐class correlation coefficient (ICC), percentage agreement, Cohen's kappa coefficients and Bland‐Altman plots. Results Estimates of daily food group servings were reliable (within 0.3 servings, P > 0.05) but not valid for all foods groups. The mean total index score was approximately 70 points (out of 100) on both SFS administrations (ICC = 0.71 (95% CI 0.56:0.81). Relative validity analysis showed moderate correlation between SFS#1 and 24‐hour recalls (ICC = 0.43 (0.21:0.62, P < 0.001)), with 51% agreement in allocation to tertiles of diet quality between methods (k = 0.262, P = 0.004). The survey overestimated the diet index score by an average of 12.7 points out of 100 [‐20.11:42.94] in comparison to recalls. Conclusions The survey overestimated compliance with guidelines relative to dietary recalls. It demonstrated good reliability; however, the validity of estimating intake of some food groups needs improvement. Future refinement will provide a valuable online tool to assess compliance with the Australian dietary recommendations.