Relative validity of a short screener to assess diet quality in patients with severe obesity before and after bariatric surgery.

OBJECTIVE: To determine the relative validity and reproducibility of the Eetscore FFQ, a short screener for assessing diet quality, in patients with (severe) obesity before and after bariatric surgery (BS). DESIGN: The Eetscore FFQ was evaluated against 3-d food records (3d-FR) before (T0) and 6 months after BS (T6) by comparing index scores of the Dutch Healthy Diet index 2015 (DHD2015-index). Relative validity was assessed using paired t tests, Kendall's tau-b correlation coefficients (τb), cross-classification by tertiles, weighted kappa values (k w ) and Bland-Altman plots. Reproducibility of the Eetscore FFQ was assessed using intraclass correlation coefficients (ICC). SETTING: Regional hospital, the Netherlands. PARTICIPANTS: Hundred and forty participants with obesity who were scheduled for BS. RESULTS: At T0, mean total DHD2015-index score derived from the Eetscore FFQ was 10·2 points higher than the food record-derived score (P < 0·001) and showed an acceptable correlation (τb = 0·42, 95 % CI: 0·27, 0·55). There was a fair agreement with a correct classification of 50 % (k w = 0·37, 95 % CI: 0·25, 0·49). Correlation coefficients of the individual DHD components varied from 0·01-0·54. Similar results were observed at T6 (τb = 0·31, 95 % CI: 0·12, 0·48, correct classification of 43·7 %; k w = 0·25, 95 % CI: 0·11, 0·40). Reproducibility of the Eetscore FFQ was good (ICC = 0·78, 95 % CI: 0·69, 0·84). CONCLUSION: The Eetscore FFQ showed to be acceptably correlated with the DHD2015-index derived from 3d-FR, but absolute agreement was poor. Considering the need for dietary assessment methods that reduce the burden for patients, practitioners and researchers, the Eetscore FFQ can be used for ranking according to diet quality and for monitoring changes over time.