The truth of responses of children, adolescents and young people participating in questionnaires regarding smoking performed in schools

BACKGROUD: The prevalence of tobacco consumption in scholars has been deter mined by self-governed inquiries, methodology that presents limitations of reliability and validity. This obstacle has been endeavoured to overcome th rough methodological inspections such as the test-retest valuation. On the contrary, the available analytical methods (i. e., determination of cotinin e in urine or determination of carbon monoxide [CO] in exhaled air) have no t been used up to now in this type of studies. Their use together with the inquiries could complement the results of the questionnaires and verify the ir reliability. POPULATION AND METHODS: 814 scholars took part in the survey, being valid t he results of 809, 385 male students and 424 female students, 13 to 24 year s old (mean 15.90, SD 1.73) from an urban high school and another in the ru ral area. The survey included a survey and the measurement of CO levels in exhaled air in the same scholar centre. RESULTS: 257 scholars stated that they had never tried tobacco and in 15 of them (5.8%) levels of CO were equal or higher than 10 ppm (14.26, SD 4.35 ppm). 589 students stated that were not regular smokers; in 46 of them (7.8 %) levels of CO were superior to 10 ppm (13.87, SD 4.68). The morning when the survey was held 629 students assured that they had not smoked: in 52 of them (8.3%) levels of CO higher than 10 ppm were observed. The mean level of CO observed in these students was 13.5 (SD 4.4) ppm. In our survey, the measurement of CO in exhaled air allowed us to show percentage between 5.8 and 8.3% of students whose answers to the different questions were not reli able. CONCLUSIONS: The reliability of the results, observed through the carrying out of surveys, can be determinated with the use of analytical methods that , owe to their simplicity, can be used massively. We have not found any rel ation between the shortage of reliability and the variants studied (age, se x or habitat), which reaffirms the difficulty in identifying variants that can determine those "deceives" and demands for its identification the need of practicing analytical determinations.