[Validity of food and beverage intake data obtained by telephone survey]

To evaluate the reproducibility and validity of data on food and beverage intake obtained by means of a telephone-based surveillance system.

Reproducibility and validity analyses were carried out in two random subsamples (n=112 and n=119, respectively) of the total sample (N=2,024) of adults (> or =18 years) studied by the system in 2005 in the municipality of São Paulo, Southeastern Brazil. Indicators evaluated included protective factors (daily or almost daily intake of fruit and vegetables) and risk factors (daily or almost daily intake of soft drinks, frequent intake of foods containing saturated animal fat, and abusive intake of alcoholic beverages) for the development of chronic diseases. Reproducibility was studied by comparing the results of the original telephonic interview with those of another interview carried out 7-15 days later. Validity was analyzed by comparing the results of the telephone interview with those of three 24-hour recalls (our gold-standard) carried out up to 5 days following the original interview.

The frequency of the studied indicators remained relatively constant between the first and second telephone interviews, with kappa coefficients ranging from 0.57 to 0.80, indicating good reproducibility for all indicators. In relation to the gold standard, there was a trend towards overestimating the frequency of intake of protective foods, but of foods associated with increased risk of chronic diseases. Sensitivity and specificity were high for indicators of consumption of risk-associated foods (close to 80%), and variable in the case of protective foods (42% to 80%).

The evaluation showed evidence of good reproducibility and adequate validity for most indicators employed in the system, which indicates that maintaining this system operational in coming years will provide a useful instrument for evaluating public policies for the promotion of a healthy diet and for control of non-communicable chronic diseases with a dietary component in Brazil.