Total body protein in healthy adolescent girls: validation of estimates derived from simpler measures with neutron activation analysis.
BACKGROUND
Little recent and accurate information about body protein content in healthy adolescent girls is available.


OBJECTIVE
The objective was to assess the total body nitrogen (TBN) and total body protein (TBPr) contents of fat-free mass (P:FFM) in a group of healthy adolescent girls and to validate previously published TBN prediction equations.


METHODS
TBN was measured with in vivo neutron activation analysis (TBNNAA). Bone mineral density and FFM were measured with dual-energy X-ray absorptiometry (FFMDXA), total body water and FFM were measured with bioimpedance analysis, and FFM was assessed by measuring skinfold thicknesses in 51 girls with a mean (+/- SD) age of 14.7 +/- 0.7 y. The validity of the TBN prediction equations was assessed with Bland-Altman analysis.


RESULTS
TBNNAA in our adolescent group was higher (1.49 kg) than values reported in earlier studies of women (1.25 and 1.31 kg), and P:FFM was slightly higher (23%) than that documented in adults (19-21%). Previously published TBN equations showed either systematic bias or wide limits of agreement.


CONCLUSIONS
A predictive equation derived from the present study population based on FFMDXA improves the prediction of TBN for groups of young girls but may not be helpful for individuals in clinical settings.
Haas
Verena K
VK
Department of Adolescent Medicine, the Children's Hospital at Westmead, Sydney, Australia.
Allen
Jane R
JR
Kohn
Michael R
MR
Clarke
Simon D
SD
Zhang
ShuHua
S
Briody
Julie N
JN
Gruca
Margie
M
Madden
Sloane
S
Müller
Manfred J
MJ
Gaskin
Kevin J
KJ
D015502:Absorptiometry, Photon; D000293:Adolescent; D000886:Anthropometry; D001823:Body Composition / Q000502:physiology*; D001827:Body Height / Q000502:physiology; D001834:Body Water / Q000378:metabolism; D001835:Body Weight / Q000502:physiology; D015519:Bone Density / Q000502:physiology; D017097:Electric Impedance; D005260:Female; D006801:Humans; D018482:Muscle, Skeletal / Q000378:metabolism*; D009501:Neutron Activation Analysis; D009584:Nitrogen / Q000378:metabolism; D011237:Predictive Value of Tests; D011506:Proteins / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D011506:Proteins; D009584:Nitrogen