A NEW CHEMICAL DIAGNOSTIC METHOD FOR INBORN-ERRORS OF METABOLISM BY MASS-SPECTROMETRY - RAPID, PRACTICAL, AND SIMULTANEOUS URINARY METABOLITES ANALYSIS

In most developed countries, neonatal mass screening programs for the early diagnosis of inborn errors of metabolism (IEM) have been impleme nted and have been found to be effective for the prevention or signifi cant reduction of clinical symptoms such as mental retardation. These programs rely primarily on simple bacterial inhibition assays(the ''Gu thrie tests''). We developed a new method for screening IEM using GC/M S, which enables accurate chemical diagnoses through urinary analyses with a simple practical procedure. The urine sample preparation for GC /MS takes one hour for one sample or three hours for a batch of 30 sam ples (will be fully automated shortly), and the following GC/MS measur ement is completed within 15 min per sample. This method allows the si multaneous analyses of amino acids, organic acids, sugars, sugar alcoh ols, sugar acids, and nucleic acid bases. Therefore, a large number of metabolic disorders can be simultaneously tested by this chemical dia gnostic procedure. This method is quite comprehensive and different fr om conventional GC/MS organic acidemia screening procedures, which are not well-suited to detect metabolic disorders except organic aciduria s. Sample preparation includes urease treatment, deproteinization, and derivatization. The method has also been applied to neonate urine spe cimens that are absorbed into filter paper. The air-dried samples were mailed to the analytical laboratory and eluted with water. The eluate (0.1 mL) was incubated with urease, followed by deproteinization with alcohol, evaporation to dryness of the supernatant, and trimethylsily lation; the samples were applied to GC/MS. A pilot study of the applic ation of this diagnostic procedure to the neonatal mass screening of 2 2 disorders was started in Japan on February 1, 1995 in cooperation wi th four medical institutes. This program is supported by the Japanese Society for Biomedical Mass Spectrometry and the Japanese Mass Screeni ng Society. The initial twenty-two target metabolic diseases are: meth ylmalonic acidemia; propionic acidemia; isovaleric acidemia; maple syr up urine disease; beta-ketothiolase deficiency; galactosemia; phenylke tonuria; hyperphenylalaninemia; homocystinuria; alkaptonuria; multiple carboxylase deficiency; nonketotic hyperglycinemia; lysinuria; cystin uria; tyrosinemia; glutaric aciduria type I; beta-hydroxy-beta-methylg lutaric acidemia; beta-methylcrotonylglycinuria; alpha-aminoadipic-alp ha-ketoadipic aciduria; ornithine transcarbamylase deficiency (four ur ea cycle disorders can be screened); glutaric aciduria type II; and ne uroblastoma. Neuroblastoma is not an IEM, and is examined at ca. 6 mon ths of age. The twenty-two target diseases will be reconsidered during the pilot study. An accurate chemical diagnosis and hence early treat ment of not only organic acidemias bur also amino acidpmias, and sugar -, polyol-, and nucleic acid base-accumulating metabolic disorders can be made at a very early stage of life. This procedure is also applica ble to metabolic profiling of other body fluids that are potentially i nformative for the study and characterization of a wide range of inher ited and acquired metabolic disorders. (C) 1997 John Wiley & Sons, Inc .