title: Validation of a semi-quantitative adolescent food frequency questionnaire applied at a public school in São Paulo, Brazil.
abstract: OBJECTIVE
  To develop a food frequency questionnaire for adolescents (AFFQ) and demonstrate its relative validity.
  
  
  METHODS
  The final version of the AFFQ was composed of 76 food items previously identified according to their contribution in nutrients and overall importance within the eating habits of this population group. The validation study, which was undertaken during a 6 month period (June to November 1999), was administered to a sample of 79 who answered at least three 24 h dietary recalls (R24 h) applied at intervals of 45 days and one AFFQ at the end of the study. Applying the paired t-test and calculating Pearson correlation coefficients on nutrient data, differences in the mean of nutrients were obtained. Correlation coefficients between the mean energy-adjusted nutrients computed by the two methods were calculated, and correction was made for within-person variability. Agreement was evaluated by distribution of the adolescents according to quartiles of consumption. LOCUS: A public school within the metropolitan region of São Paulo city.
  
  
  RESULTS
  A high variability in the dietary intake of adolescents was observed, with high rates of variability for cholesterol, retinal and vitamin C. The Pearson correlation coefficients, after being adjusted and corrected for variability, ranged from 0.10 to 0.72 among females and from 0.16 and 0.91 among males. The mean correlation coefficient for the entire group was 0.52.
  
  
  CONCLUSIONS
  These results indicate that the AFFQ provides a potentially reliable scale for categorizing individuals by level of past intake of most nutrients, excluding retinol and iron.
authors.affiliation: Department of Nutrition, School of Public Health, University of São Paulo, São Paulo, Brazil. betzy_slater@hotmail.com
authors.forename: B
authors.initials: B
authors.lastname: Slater
authors.forename: S T
authors.initials: ST
authors.lastname: Philippi
authors.forename: R M
authors.initials: RM
authors.lastname: Fisberg
authors.forename: M R D O
authors.initials: MR
authors.lastname: Latorre
mesh_terms: D000293:Adolescent; D001205:Ascorbic Acid / Q000008:administration & dosage; D001938:Brazil; D002136:Calcium, Dietary / Q000008:administration & dosage; D002791:Cholesterol, Dietary / Q000008:administration & dosage; D004032:Diet; D015930:Diet Records; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D004042:Dietary Fats, Unsaturated / Q000008:administration & dosage; D004043:Dietary Fiber / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D002149:Energy Intake; D005260:Female; D005518:Food Preferences; D006801:Humans; D019266:Iron, Dietary / Q000008:administration & dosage; D008297:Male; D015596:Nutrition Assessment; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D014801:Vitamin A / Q000008:administration & dosage
chemical_list: D002136:Calcium, Dietary; D002791:Cholesterol, Dietary; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004042:Dietary Fats, Unsaturated; D004043:Dietary Fiber; D004044:Dietary Proteins; D019266:Iron, Dietary; D014801:Vitamin A; D001205:Ascorbic Acid