Reliability and relative validity of an FFQ for nutrients in the Tehran Lipid and Glucose Study

TLDR

The study aims to assess the relative validity and reliability of a 168‑item FFQ for measuring nutrient intake in Tehran Lipid and Glucose Study participants. The authors evaluated the FFQ by comparing it with monthly 24‑hour dietary recalls and biochemical biomarkers in 132 TLGS participants, using two 168‑item semi‑quantitative FFQs and seasonal blood/urine samples. The FFQ showed moderate validity (correlation coefficients 0.24–0.71 for nutrients) and reliability (coefficients 0.41–0.79), with agreement rates of 39–68 % in men and 39–54 % in women, indicating reasonable relative validity and reliability for nutrient intake assessment.

Abstract

ObjectiveTo describe the relative validity and reliability of the FFQ used for assessing nutrient intakes of participants in the Tehran Lipid and Glucose Study (TLGS).DesignA total of 132 subjects (sixty-one males and seventy-one females) were included in the study. Dietary data were collected monthly by means of twelve 24 h dietary recalls (24hDR). Subjects completed two, 168-item semi-quantitative FFQ. Blood and urine samples were taken every season for measurement of plasma biomarkers and urinary N and K.ResultsMean age and BMI of the participants were 35·5 (sd 16·8) years and 25·5 (sd 5·2) kg/m2, respectively. The mean energy-adjusted and deattenuated correlation coefficients for overall nutrient intake between the 24hDR and FFQ2 were 0·44 and 0·37 in ≤35-year-olds and >35-year-olds, respectively, and for individual nutrients ranged from 0·24 to 0·71 in men (mean r = 0·53) and from 0·11 to 0·60 in women (mean r = 0·39). The mean energy-adjusted reliability coefficients varied from 0·48 in ≤35-year-olds to 0·65 in >35-year-olds, and ranged from 0·41 to 0·79 in men (mean r = 0·59) and from 0·39 to 0·74 in women (mean r = 0·60). The FFQ2 and 24hDR produced exact agreement rates ranging between 39·6 % and 68·3 % in men and between 39·6 % and 54·1 % in women. The ranges of questionnaire validity coefficients, with the sample correlation between the questionnaires and biochemical marker as the lower limit and the estimate obtained by the method of triads as the upper limit, were 0·21–0·56 (protein) and 0·37–0·61 (K).ConclusionsThe FFQ developed for the TLGS has reasonable relative validity and reliability for nutrient intakes in Tehranian adults.