Clinical chemistry
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Disorders of creatine metabolism arise from genetic alterations of arginine:glycine amidinotransferase (AGAT), guanidinoacetate methyltransferase (GAMT), and the creatine transporter. We developed a strategy for the detection of AGAT and GAMT defects by measurement of guanidinoacetate (GAA) and creatine plus creatinine (Cr+Crn) in biological fluids. ⋯ The assessment of GAA is a new tool for the detection of both GAMT and AGAT deficiencies.
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The determination of organic acids and glycine conjugates in urine is key for the diagnosis and follow-up of several inborn errors of metabolism (IEM). However, clinical interpretations may still be hindered by ambiguity in the sources of some urinary organic acids and acylglycines as well as in the relationship between their excretion and IEM. ⋯ A comprehensive table has been designed according to organic acids and conjugates. This table is intended to assist in the interpretation of organic acid profiles because, in addition to IEM, it also refers to other pathologic causes and to physiologic, nutritional, iatrogenic, and artifactual sources. Some preanalytical issues, including possible misinterpretations, are reviewed with regard to IEM.
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Editorial Comment
Practice guidelines and practicing physicians-who's guiding whom?