Reproducibility and validity of a culture specific food frequency questionnaire for assessing dietary intake in the adult population of Trinidad and Tobago

Abstract Background Nutritional epidemiologists use culture-specific food frequency questionnaires (FFQs) to assess the dietary intake of groups based on country, region or ethnic groups. The aim of this study was to assess the performance of a self-constructed culture-specific semi-quantitative electronic FFQ (e-FFQ) in assessing food group intake estimates when compared with multiple 1-day food records (FRs) for the adult population of Trinidad and Tobago. Methods The 139-item semi-quantitative e-FFQ containing local dishes and street foods was created using Google forms. It was emailed twice, 3 months apart, to 91 participants ≥ 18 years of age. The first administration of the e-FFQ was validated against 4-four one-day FRs with digital photographs which served as the reference method. Using SPSS Version 26, the validity and reproducibility of the FFQ’s food group intake estimates were determined using paired t-tests, bivariate correlations, and cross-classifications. Cross-classification and Bland-Altman plots were used to show agreement between the e-FFQ and weighted mean of the FRs. Results Participants consisted of 22% males and 78% females, mean age 38 ± 9.6 years. Reproducibility correlations between the reported food group intakes in the first and repeat administration of the e-FFQ ranged from moderate (r = 0.44 p ≤ 0.0001) for sweetened beverages to high (r = 0.91 p ≤ 0.0001) for alcohol. Cross-classification agreements within ± 1 quintile ranged from 70% (street foods) to 92% (alcohol). Crude validity correlations between the e-FFQ and FR ranged from (r = 0.06) for sweets to (r = 0.65) for food from animal sources, with mean of the validity correlations being 0.34. Deattenuated correlations ranged from r = 0.11 for sweets to r = 0.81 for food from animal sources. Cross-classification showed that an average of 68% of the FFQ estimates were correctly classified within ± 1 quintile of exact agreement in the FRs. Agreements between the FFQ and the FRs ranged from 55% for street foods to 95% for water, all significant at p ≤ 0.0001. Conclusions The study shows that this culture-specific e-FFQ is highly reproducible and is a reasonably valid tool to assess and rank food group intake estimates of an adult population living in Trinidad and Tobago. Thus, it can be used to examine associations between dietary intakes and NCDs.