Validity and reliability of a questionnaire measuring EBDPs among registered dietitian nutritionist

Background: There is a lack of a valid and reliable instrument that measures objective and subjective knowledge of evidence-based dietetic practices (EBDP) among registered dietitian nutritionists (RDNs). The present study aimed to develop and assess the validity and reliability of an EBDP Questionnaire (EBDPQ) with objective knowledge items (i.e., quiz items) among RDNs in the USA. Methods: Subscales from four existing evidence-based practice (EBP) instruments were combined and modified for dietetics. Content and face validity and internal consistency were used to assess the full survey. Survey responsiveness and test–retest reliability were evaluated within the objective knowledge subscale. Content experts (n = 11) and nutrition professionals (n = 16) completed validation reviews. Doctoral students enrolled in a research course (n = 12) were used to analyse survey responsiveness. Internal and test–retest relability analyses utilised RDN participants (time point 1, n = 482; time point 2, n = 335). Results: Content validation resulted in a 38-item questionnaire. Average percent agreement among face validity reviewers was 95.1%. Only the pre-validation version of the objective knowledge subscale resulted in significantly higher post-course scores (Mdn = 11.50) compared to the pre-course (Mdn = 9.75, p = 0.05). The validated instrument had excellent internal consistency (Cronbach's α = 0.91); however, the objective knowledge subscale was low (Cronbach's α = 0.41). A good degree of reliability was found between the two time points (intraclass correlation coefficient = 0.71). Conclusions: The EBDPQ demonstrated adequate validity and reliability among RDNs. Future research should assess construct validity, with the responsiveness and objective knowledge subscale requiring additional evaluation through an EBDP course.