Development, validity and reliability of the street food and beverage tool.

Objective: To develop and evaluate the validity and reliability of the Street Food and Beverage Tool (SFBT).

Design: This methodological study contains two phases: (a) tool development, which involves conducting a systematic review followed by expert evaluation of the items, the creation of a nutritional healthfulness index (NH), and pilot testing; and (b) evaluation of the Tool's Validity and Reliability. Content validity was judged by an external technical group, which evaluated the adequacy and pertinence of each tool item. Construct validity was evaluated around schools by testing the hypothesis: In high-income areas, there will be greater availability of healthy food and beverages at street food outlets (SFO), as measured by the NH index. Inter-rater and test-retest reliabilities were assessed outside subway stations. Pearson's correlation, Cohen's kappa and Content validity Indexes were used for reliability and validation. A multinomial regression model was used to estimate construct validity.

Setting: Mexico City, Mexico.

Participants: 80 SFO at subway station exits and 1066 around schools from diverse income areas.

Results: The SFBT content validity index was satisfactory. The construct validity of the NH index indicated higher values in higher-Social Development Index areas. The NH index showed a positive linear correlation between raters and across the first and second evaluations. The majority of item availability (>60 %) showed moderate to strong kappa values for inter-rater and test-retest reliability.

Conclusions: The SFBT is a reliable and valid tool for assessing the availability of foods and beverages. Compared to other tools, it can measure the nutritional quality of SFO expressed as an NH index.