Background: Information about the reliability and validity of questionnaires in low- and middle-income countries remains scarce. Objective: To test the reliability and predictive validity of a food and beverage marketing/advertising questionnaire for South American children and adolescents. Methods: A sample of 330 children (3-10 years old) and 215 adolescents (11-18 years old) was included from seven South American cities: Buenos Aires, Lima, Medellín, Montevideo, Santiago, Sao Paulo, and Teresina. The questionnaire consisted of seven questions about food and beverage marketing/advertising and decision influence. We assessed the reliability using temporal stability (2-week interval) and internal consistency. We assessed the predictive validity based on the risk of excess weight. Results: In children, reliability agreement from κ coefficients ranged from 63.7% to 86.3%, and Cronbach's α (internal consistency estimate) ranged from 0.14 to 0.75. In adolescents, the reliability agreement ranged from 78.9% to 85.7%, and Cronbach's α ranged from 0.14 to 0.76. Exploratory factor analysis revealed two factors for both age groups. The predictive probabilities for excess weight ranged from 22.3% to 61.1% in children and from 24.9% to 64.1% in adolescents. Conclusions: The screen/marketing media questionnaire is a reliable and valid measure for the pediatric population from low- and middle-income countries. This subjective tool provides a feasible screening measure for the influence of advertising on children and adolescents at risk of overweight and obesity.
Keywords: epidemiology; food and beverage marketing; obesity; pediatrics.