Stable isotopes in the management and diagnosis of inborn errors of metabolism.

Stable isotope techniques offer advantages over older methods in safety, sensitivity, specificity, and reduction in number of subjects required for analytic determinations in some types of studies in "inborn errors of metabolism." In addition to their use as internal standards for gas chromatography - mass spectrometry, quantitation of plasma substrates, and their urinary metabolites, stable isotopes have been successfully employed in studies of metabolite identification, enzyme activity, nutrient turnover and requirements, and diagnosis of inborn errors of metabolism.