title: Performance of references based on body mass index for detecting excess body fatness in schoolchildren aged 7 to 10 years.
abstract: OBJECTIVE
  To compare the sensitivity and specificity of body mass index (BMI)-based classification systems and to determine the optimal cut-offs for predicting excess body fatness in schoolchildren.
  
  
  METHODS
  2795 schoolchildren aged 7 - 10 years were examined. Excess body fatness was defined as the standardized residuals of the sum of three skinfold thickness ranking at or above the 90th percentile. The international BMI-based system recommended by the World Health Organization (WHO-2007) was evaluated on the basis of its sensitivity and specificity for detecting excess body fatness and compared with a national BMI reference (Brazil-2006). Likelihood ratios analysis was used to select the optimal cut-offs in each curve.
  
  
  RESULTS
  The two classification systems presented high sensitivity (92.5 - 98.6%) and moderate specificity (75.9 - 85.0%) for both sexes. The optimal BMI cut-offs improved specificity with no marked loss of sensitivity. Using the proposed BMI cut-offs, the post-test probability of predicting excess body fatness for children classified as non-overweight decreased from 10 (pre-test probability) to 1.4% in girls and to 1.1% in boys. For overweight children, this probability increased to more than 46.0%.
  
  
  CONCLUSIONS
  The results showed that both the WHO-2007 and Brazil-2006 classification systems can be used as screening instruments for excess body fatness, and that one of the limitations of using the BMI-for-age references could be improved by refining the existing cut-offs.
authors.affiliation: Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
authors.forename: Danielle Biazzi
authors.initials: DB
authors.lastname: Leal
authors.affiliation: Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
authors.forename: Maria Alice Altenburg
authors.initials: MA
authors.lastname: de Assis
authors.affiliation: Department of Nutrition, School of Public Health, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Wolney Lisboa
authors.initials: WL
authors.lastname: Conde
authors.affiliation: INRA, SMBH Universite' Paris13, Paris, France.
authors.forename: France
authors.initials: F
authors.lastname: Bellisle
mesh_terms: D000273:Adipose Tissue; D015992:Body Mass Index; D001938:Brazil; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D050177:Overweight / Q000175:diagnosis*; D012016:Reference Values; D012680:Sensitivity and Specificity