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Training Module: Using the BMI-for-Age Growth Charts

Recommended BMI-for-age cutoffs
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SENSITIVITY, SPECIFICITY, AND VALIDITY OF BMI-FOR-AGE AS A TOOL TO SCREEN CHILDREN FOR INCREASED ADIPOSITY

High BMI-for-age among children and teens correlates with excess adiposity (Mei et al 2002; Pietrobelli et al., 1998) and cardiovascular disease risk factors (Freedman and Sherry, 2009; Freedman et al., 2007). The accuracy of BMI-for-age as an indicator of body fatness varies according to the degree of body fatness, and “its accuracy increases with the degree of body fatness” (Freedman and Sherry, 2009; p. S27). Analyses of data from the Pediatric Rosetta Project showed that a high BMI-for-age (≥95th CDC percentile) is a good index of excess body fatness for both girls and boys (Freedman et al., 2005), and at the high BMI cut points (≥95th percentile), BMI-for-age has moderately high sensitivity and positive predictive values, as well as a high specificity for identifying children with excess body fatness (Freedman and Sherry, 2009, p. S31). Freedman, Wang, Thornton, and colleagues (2009) showed that levels of body fatness among children who had a BMI-for-age between the 85th and 94th percentiles are variable; only 30% of children classified as overweight have normal body fatness. Because BMI does not measure body fat directly and may lead to imprecise assessment of adiposity, BMI-for-age is not considered diagnostic of body fatness (Freedman, Wang, Thornton, et al., 2009). This is especially true for children classified as overweight.

 

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