Ability of biolectric impedance to predict fat-free mass in prepubertal children.

Measurements of body composition are being made increasingly widely in pediatrics. Tetrapolar whole body impedance (BI) is particularly suitable as a method of estimating body composition in children and is therefore the subject of great interest at present. However, the ability of BI to accurately estimate fat-free mass (FFM) in children is unclear, and users of BI are faced with a growing choice of prediction equations for estimation of FFM. Studies in adults have suggested that choice of prediction equation can have a profound effect on the estimate obtained. The aim of the present study was to measure the ability of four published pediatric BI equations to predict FFM in 98 Caucasian prepubertal children (mean age 9.0 y). For three of the published equations, limits of agreement between predicted and reference FFM were wide and distinct biases were apparent. With mean FFM of 25 kg, the equation of L. Cordain et al. overestimated reference FFM (95% CI +2.1 to +3.1 kg), whereas those of P. Deurenberg et al. (95% CI -1.9 to -2.9 kg) and F. Schaefer et al. (95% CI -1.4 to -2.5 kg) systematically underestimated reference FFM. The equation of Houtkooper et al. (95% CI -0.2 to +0.8 kg) predicted FFM with negligible bias and had narrower limits of agreement relative to the reference method than the other three equations tested. We conclude that the ability of BI to predict body composition in children depends on the equation chosen and that the general applicability of BI equations cannot be safely assumed. Cross-validation of BI equations is recommended before they are used routinely for estimation of body composition in children.

There are few data on the prevalence of viral infections and their distinguishing features in children with cancer who are hospitalized for fever and chemotherapy-induced neutropenia. Between August, 1994 and August, 1995 we prospectively followed 40 such children hospitalized for fever and neutropenia. Nasal and pharyngeal swabs for viral culture and pre- and post-convalescent sera were obtained on all the children. There were 76 episodes of fever and neutropenia in the 40 children. Viral infection was documented in 26 of the 76 episodes (34%) (6 rhinovirus, 6 parainfluenza, 5 RSV, 3 VZV, 2 coronavirus, 2 influenza B, 1 enterovirus, and 1 rhinovirus + parainfluenza). Culture-proved bacterial or fungal infections were found in an additional 14 episodes (18%). There were no significant differences in exposure to illness, site of childcare, respiratory signs and symptoms, height of fever, days of fever, absolute neutrophil count, days to recovery of the absolute neutrophil count, or days hospitalized for the children with viral infections versus those children with culture-proved bacterial or fungal infections or those with no documented source of infection. Viral infection was the most common identifiable cause of infection in children hospitalized For fever and neutropenia. There were no clinical features which distinguished this group of children from those children with bacterial/fungal infection or no culture-proved infection. Laboratory diagnosis with nasopharyngeal cultures is essential to identify these children and may be helpful in the management of their febrile illnesses.