Sensitivity and specificity of body mass index-based classification systems for overweight in children 7-10 years old.

Abstract

The objective of this study was to compare the sensitivity and specificity of BMI-based classification systems for detecting excess body fat in schoolchildren. A total of 2,795 schoolchildren aged 7 to 10 years were examined. Excess body fat was defined as the standardized residuals of sum of three skinfolds thickness ranking at or above the 90th percentile. The international BMI-based systems recommended by the International Obesity Task Force (IOTF) and the World Health Organization(WHO-2007) were evaluated on the basis of their sensitivity and specificity for detecting excess body fat and compared with a national BMI reference (Brazil-2006). The positive (LR+) and negative (LR-) likelihood ratios analysis was also used to compare the diagnostic accuracies of the three BMI criteria.The three classification systems presented moderately high sensitivity (78.4-98.6%) and specificity (75.9-91.6%) for both genders. Overall, the three classification systems showed both LR+ and LR- values consistent with adiagnosis of moderate evidence for overweight (LR+ above five and LR- below0.2). The results showed that the three BMI classification systems can be usedas screening instruments of excess body fat. However, the performance of the Brazil-2006 classification system was superior because it showed the best balance between the diagnostic accuracy indices.