Structure and Preliminary Reliability of the Diet Quality Questionnaire (DQQ)-Based Form Adapted for Use in the Polish Population—Results from Initial Validation Stage

Background/Objectives: The Diet Quality Questionnaire (DQQ) is a brief, food group–based instrument designed for globally comparable population surveillance of diet quality. We culturally adapted the DQQ for Poland and evaluated its internal structure and reliability in an adult cohort. Methods: Following forward–backward translation and expert review, the Polish DQQ was administered online to adult females. Internal structure was explored and test–retest reliability was assessed for total DQQ scores. Diet quality indicators (Dietary Diversity Score DDS, NCD-protect, NCD-risk, and Global Dietary Recommendations score GDR) were summarized descriptively. Results: The average age in the cohort was 29.4 ± 13.6 years. A total of 296 respondents completed the survey; 100 completed the retest. Item-level test–retest reliability was good to excellent (Cohen’s kappa 0.72–1.00). Agreement for total scores was high with minimal bias (Bland–Altman bias 0.2, >95% of observations within limits of agreement) and there was no heteroscedasticity; Passing–Bablok regression indicated equivalence between the test and retest. Median (IQR) diet quality indicators were: DDS 6.0 (5.0; 7.0), NCD-protect 2.5 (1.5; 4.0), NCD-risk 2.5 (1.0; 4.0), and GDR 9.0 (7.5; 10.5). Eighty percent met DDS ≥ 5, while one-third consumed all five recommended food groups. Conclusions: DQQ-PL demonstrates high item-level stability and strong agreement for total scores, with structural findings aligning with its design as a non-latent, food group checklist for population monitoring. The Polish adaptation is feasible and reliable in the studied population (young adult women), supporting its potential use for rapid dietary surveillance pending broader validation.