THE VALIDITY OF BODY-MASS INDEX FOR THE ASSESSMENT OF ADIPOSITY IN CHILDREN WITH DISEASE STATES

Recently published standards for body mass index (BMI) based on popula tion studies of height and weight in healthy British children allow an easy but indirect assessment of adiposity in healthy children. Howeve r, assessment of adiposity based on standards derived From reference p opulations may not be appropriate for use in subjects with disease sta tes associated with abnormalities of growth and body composition. This hypothesis was tested by comparison between BMI standard deviation sc ores (SDS) and more direct measures of body fat derived from dual-ener gy X-ray absorptiometry (DEXA) and skinfold thickness in groups of chi ldren, receiving growth hormone, with inflammatory bowel disease, prev iously treated for malignancy, and healthy controls. Excess adiposity was defined as a body fat greater than the 85th percentile and was com pared to a BMI SDS of + 1.0. Overall the sensitivity and specificity f or a BMI SDS of + 1.0 to correctly identify individuals as having exce ss adiposity was 66% and 94%, respectively, when body fat was measured by DEXA, and 50% and 100% when estimated from skinfold measurements, respectively. There were no significant differences in these statistic s whether applied to the individual disease groups or to healthy contr ols. These findings suggest that BMI under-predicts the prevalence of excess adiposity in children with disease states but surprisingly to n o greater degree than that seen in healthy subjects.