Development and validation of the Dental Nutrition Knowledge Competency Scale for low-income women.

OBJECTIVE: To develop and validate a Dental Nutrition Knowledge Competency Scale to assess dental health-related nutrition knowledge of low-income women. DESIGN: This is a cross-sectional study. A literature search for foods/dietary practices related to dental caries was conducted and the items were incorporated into an initial questionnaire. A panel of ten nutrition experts evaluated it for its content, readability and relevance, and a focus group of six low-income women determined its readability and comprehension. Then the questionnaire was administered to 150 low-income women. Construct validity was evaluated by item difficulty, item discrimination and factor analysis. Internal consistency reliability was tested via Cronbach's α. In a sub-sample of forty women, test-retest reliability was established. Paired-sample t tests were conducted to examine differences between test scores at the two time points, 2 weeks apart. SETTINGS: Community centres in low-income housing in Central Texas, USA. PARTICIPANTS: A total of 150 low-income women, aged 18-50 years; annual household income <250 % of the federal poverty level. RESULTS: Item difficulty and discrimination analysis resulted in elimination of eight questions. Factor analysis identified twenty-four items that loaded on three factors related to knowledge. These included foods/dietary practices that affect dental caries, added sugars in foods and on food labels, and recommended frequency of oral hygiene practices. The subscales and the completed scale exhibited good internal consistency (mean 0·7 (sd 0·97)) and test-retest reliability (mean 0·8 (sd 0·013)). CONCLUSIONS: The Dental Nutrition Knowledge Competency Scale is a validated and reliable instrument to assess nutrition knowledge related to dental health in low-income women.