Rapid Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry Assay for a Characteristic Glycogen-Derived Tetrasaccharide in Pompe Disease and Other Glycogen Storage Diseases

BACKGROUND: Urinary excretion of the tetrasaccharide 6-alpha-D-glucopyranosyl-maltotriose (Glc(4)) is increased in various clinical conditions associated with increased turnover or storage of glycogen, making Glc(4) a potential biomarker for glycogen storage diseases (GSD). We developed an ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay to detect Glc(4) in urine without interference of the Glc(4) isomer maltotetraose (M-4). METHODS: Urine samples, diluted in 0.1% ammonium hydroxide containing the internal standard acarbose, were filtered, and the filtrate was analyzed by UPLC-MS/MS. RESULTS: We separated and quantified acarbose, M-4, and Glc(4) using the ion pairs m/z 644/161, 665/161, and 665/179, respectively. Response of Glc(4) was linear up to 1500 mu mol/L and the limit of quantification was 2.8 mu mol/L. Intra- and interassay CVs were 18.0% and 18.4% (10 mu mol/L Glc(4)), and 10.5% and 16.2% (200 mu mol/L Glc(4)). Glc(4) in control individuals (n = 116) decreased with increasing age from a mean value of 8.9 mmol/mol to 1.0 mmol/mol creatinine. M-4 was present in 5% of CONCLUSIONS: The UPLC-MS/MS assay of Glc(4) in urine was discriminative between Glc(4) and M-4 and confirmed the diagnosis in >98% of GSD-II cases. (c) 2012 American Association for Clinical Chemistr