WHEN evaluating clinical chemical data from small children, it is important to realize that the normal values and ranges of the concentrations of several serum constituents in infants differ from those of adults. However, the mean concentrations and their variations with the age of the child are of interest not only in routine clinical work but also from an ontogenetic point of view, since these changes may contribute to the understanding of the normal development of the child. The investigation reported in this paper is an attempt to study such changes in a limited field.
In an earlier paper1 it was reported that the serum nonprotein nitrogen (NPN) and creatinine levels in newborn infants were approximately similar to adult levels, and that the respective concentrations decreased to a significantly lower level than that of adults after five or six days. From this lower level they gradually increased, reaching adult
Fürst P, Josephson B. Nonprotein Serum Nitrogen in Infancy. Am J Dis Child. 1967;113(3):345-351. doi:10.1001/archpedi.1967.02090180105009