Urinary excretion of non-nitrogenous organic acids by healthy infants and children.

For some years now, urinary amino acid screening for inborn errors of metabolism has been routine in many institutions. In the early 1960’s, Cox and White (1) as well as Barness et a!. (2) showed the importance of measuring methylmalonate excretion in the urine of patients suffering from pernicious anemia. Since that time, detection of non-nitrogenous organic acids has taken on an importance similar to that of amino acid measurement, primarily because of the discovery (3) that there are inborn errors of metabolism that result in massive excretion of organic acids. The new discovery of several hereditary diseases (including lactic acidemia, propionic acidemia, and pyruvic acidemia) has emphasized the importance of this investigation. Urine specimens offer two major advantages over blood. Not only are specimens more easily collected, but the volumes are larger.As a result,small quantities of a compound can be measured by concentrating the specimen from large volumes of urine. Previous methods have been developed to demonstrate the collective urinary organic acid pattern in patients (2), and many quantitative methods are now available to assay organic acids (4-8). In the medical literature, there are quantitative data on the excretion of organic acids, but most of these are for adults (1, 9-15), and those related to childhood values (16-26) have been limited to only a few of the detectable organic acids. Here, we describe the daily excretions of 14 organic acids by 27 normal children, as measured by a quantitative method previously described (27).