Background: There is a lack of instruments to measure the ability of health professionals to promote dietary advice according to dietary guidelines.
Aim: To develop and validate a web-based and self-applied scale for measuring primary health care (PHC) professionals' self-efficacy and collective efficacy to apply the Brazilian Dietary Guidelines for dietary advice.
Methods: Methodological procedures comprised six steps: development of the items; content validation with panel of experts; face validation through focus group conducted with PHC professionals; online reevaluation by the participants of content and face validation panels; online application with PHC professionals working all over Brazil's macro-regions; confirmatory factorial analysis to test construct validity.
Results: The scale was initially developed with 22 items. After content and face validation panels, changes in content and semantics were performed. The second version consisted of 24 items equally divided into part A (self-efficacy) and B (collective efficacy). All items, when reevaluated, were considered clear and representative of the Brazilian Dietary Guidelines' chapters. The multidimensional model was shown to have excellent fit indices in the confirmatory factorial analysis. The scale's peak of information was centered around the mean, indicating that both domains are more precise for perception of self-efficacy and collective efficacy on average values.
Conclusion: The scale demonstrated validity for measuring PHC professionals' perceived self-efficacy and collective efficacy to apply the Brazilian Dietary Guidelines. To our knowledge, this is the first valid scale for measuring the capability of PHC professionals to apply national dietary guidelines for healthy diet promotion.
Keywords: Dietary guidelines; primary health care; psychometrics; self-efficacy.