Identifying very fat and very thin children: test of criterion standards for screening test

Charts of body mass index (weight (kg)/(height (m)2)) for children have been recommended for clinical use in the United Kingdom.1 It is unclear how they are to be used, but the accompanying referral guidelines suggest that they have a place in community screening. Caution has been urged, however, when using body mass index for children of different heights.2 Data from the Wessex growth study show that 10% of short normal children—compared with 27% of controls—had a body mass index ≥75th centile at the age of 9 years (unpublished data). To determine the reason for this apparent bias, we examined the weight for height relations required for prepubertal children of different heights to have a high or low body mass index. Weights and weight standard deviation scores were calculated for children of different heights to give body mass indices ≥99.6th centile and ≤0.4th centiles. The difference between height …