cx-AMINO ACIDS IN CHILDREN

The determination of the total content of free a-amino acids in urine has become routine in paediatric practice in numerous diseases. Interest in aminoaciduria has greatly increased since it became known that many congenital metabolic disorders are accompanied by an increased excretion of free oc-amino acids in the urine (Paine, 1960; Woolf, 1961). The excretion of free a-amino-N is usually expressed quantitatively in one of the following ways: (a) mg. a-amino-N excreted per 24 hours (Huisman, 1957; Ghadimi and Shwachman, 1960); (b) mg. a-amino-N per kg. body weight per 24 hours (Huisman, 1957; Childs, 1952; Berger, 1959; Ghadimi and Shwachman, 1960); (c) mg. a-amino-N as percentage of the total nitrogen excretion in mg. per 24 hours (Huisman, 1957; Berger, 1959; Ghadimi and Shwachman, 1960); and (d) mg. ac-amino-N in relation to the creatinine excretion in mg. per 24 hours (Ghadimi and Shwachman, 1960; Fowler, Norton, Cheung, and Pratt, 1957). The absolute 24-hour excretion of amino acids is strongly dependent on age, making this way of expression inapplicable for comparison of aminoaciduria in children of various ages. The other three methods are all in use. We have made a comparative investigation of the various ways in which aminoaciduria is expressed, because so little seems to have been published on this subject.