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Quantification of N-acetyl-L-aspartic acid in urine by isotope dilution gas chromatography-mass spectrometry.

A method for quantification of N-acetyl-L-aspartic acid by isotope dilution gas chromatography-mass spectrometry using 15N-[2H3]acetyl-L-aspartic acid is described. The method is sufficiently sensitive to be used with solvent extraction techniques commonly employed for urinary organic acid analysis. The mean concentration of N-acetyl-L-aspartic acid in 80 normal and abnormal control urine specimens was 19.7 +/- 10.8 mg/g creatinine (12.7 +/- 7.8 mmol/mol creatinine). Seven patients, ages 9 months to 7 years, with Canavan-van Bogaert syndrome had urinary N-acetyl-L-aspartic acid levels from 606 to 4760 mg/g creatinine. The method can also be used with cerebrospinal fluid, in which the concentration of N-acetyl-L-aspartic acid is about one-tenth of that in urine.