Development and validation of a simple convenience store SHELF audit

Background This paper describes the development, reliability, and convergent validity of a practical tool—the Convenience Store Supportive Healthy Environment for Life-Promoting Food (SHELF) Audit. Methods Audit items included: a variety of fresh, processed, and frozen fruits and vegetables; low-fat dairy products; healthy staples and frozen meals; healthy food incentive programs; items sold in check-out areas; portion/cup sizes; and pricing. Each audit item was scored using a five-point semantic-differential scale (1 = provides little or no support for healthful foods to 5 = provides high support for healthful foods). Convergent validity was examined by comparing the SHELF audit to Ghirardelli et al. and Laska et al. store audits. Statistical analysis included: Factor analysis, ANOVA, and Spearman correlations. Results SHELF included three factors: a Fruits/Vegetables scale (eight items, α = 0.79; total potential points = 34); a Healthy Foods scale (four items, α = 0.72; total potential points = 16); and a Supports scale (four items, α = 0.685; total potential points = 16). Only 6% of the 124 convenience stores assessed scored in the most healthful range (46–66). The assessed drug stores (n = 15) scored higher than convenience stores (n = 81) on the Healthy Foods and Supports scales but not the Fruits/Vegetables scale. The SHELF sub-scores were highly correlated with other audit tools indicating convergent validity. Conclusion The SHELF convenience store audit is a valid, reliable tool for assessing the degree to which convenience stores support healthfulness regarding Fruits/Vegetables, Healthy Foods, and Supports for choosing healthy.