Construct validation of 4 food-environment assessment methods: adapting a multitrait-multimethod matrix approach for environmental measures.

Few studies have assessed the construct validity of measures of neighborhood food environment, which remains a major challenge in accurately assessing food access. In this study, we adapted a psychometric tool to examine the construct validity of 4 such measures for 3 constructs. We used 4 food-environment measures to collect objective data from 422 Ontario, Canada, food stores in 2010. Residents' perceptions of their neighborhood food environment were collected from 2,397 households between 2009 and 2010. Objective and perceptual data were aggregated within buffer zones around respondents' homes (at 250 m, 500 m, 1,000 m, and 1,500 m). We constructed multitrait-multimethod matrices for each scale to examine construct validity for the constructs of food availability, food quality, and food affordability. Convergent validity between objective measures decreased with increasing geographic scale. Convergent validity between objective and subjective measures increased with increasing geographic scale. High discriminant validity coefficients existed between food availability and food quality, indicating that these two constructs may not be distinct in this setting. We conclude that the construct validity of food environment measures varies over geographic scales, which has implications for research, policy, and practice.