In:
Clinical Chemistry, Oxford University Press (OUP), Vol. 58, No. 7 ( 2012-07-01), p. 1139-1147
Abstract:
Urinary excretion of the tetrasaccharide 6-α-D-glucopyranosyl-maltotriose (Glc4) is increased in various clinical conditions associated with increased turnover or storage of glycogen, making Glc4 a potential biomarker for glycogen storage diseases (GSD). We developed an ultraperformance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) assay to detect Glc4 in urine without interference of the Glc4 isomer maltotetraose (M4). 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, M4, and Glc4 using the ion pairs m/z 644/161, 665/161, and 665/179, respectively. Response of Glc4 was linear up to 1500 μmol/L and the limit of quantification was 2.8 μmol/L. Intra- and interassay CVs were 18.0% and 18.4% (10 μmol/L Glc4), and 10.5% and 16.2% (200 μmol/L Glc4). Glc4 in control individuals (n = 116) decreased with increasing age from a mean value of 8.9 mmol/mol to 1.0 mmol/mol creatinine. M4 was present in 5% of urine samples. Mean Glc4 concentrations per age group in untreated patients with Pompe disease (GSD type II) (n = 66) were significantly higher, ranging from 39.4 to 10.3 mmol/mol creatinine (P & lt; 0.001–0.005). The diagnostic sensitivity of Glc4 for GSD-II was 98.5% and the diagnostic specificity 92%. Urine Glc4 was also increased in GSD-III (8 of 9), GSD-IV (2 of 3) and GSD-IX (6 of 10) patients. CONCLUSIONS The UPLC-MS/MS assay of Glc4 in urine was discriminative between Glc4 and M4 and confirmed the diagnosis in & gt;98% of GSD-II cases.
Type of Medium:
Online Resource
ISSN:
0009-9147
,
1530-8561
DOI:
10.1373/clinchem.2011.178319
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
2012