ABSTRACT
BACKGROUND: 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 < 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 >98% of GSD-II cases.
Subject(s)
Glycogen Storage Disease/urine , Glycogen/metabolism , Oligosaccharides/urine , Adolescent , Adult , Age Factors , Aged , Child , Child, Preschool , Chromatography, Liquid , Glycogen Storage Disease Type II/urine , Glycogen Storage Disease Type III/urine , Glycogen Storage Disease Type IV/urine , Humans , Infant , Infant, Newborn , Maltose/analogs & derivatives , Maltose/urine , Middle Aged , Reference Values , Spectrometry, Mass, Electrospray Ionization , Tandem Mass Spectrometry , Young AdultSubject(s)
Glycogen Storage Disease/urine , Liver Glycogen/metabolism , Oligosaccharides/urine , Child , Child, Preschool , Chromatography, Gas , Chromatography, Gel , Chromatography, Thin Layer , Glycogen Storage Disease Type II/urine , Glycogen Storage Disease Type III/urine , Glycogen Storage Disease Type IV/urine , Humans , InfantABSTRACT
Three urine samples were distributed to laboratories in the Trent and Yorkshire regions to assess their ability to detect glycosaminoglycans. Satisfactory results were obtained for samples from patients with Hunter's and Morquio's diseases but six of 14 laboratories reporting a result for a Sanfilippo sample missed the abnormality. Replies to a subsequent questionnaire showed that unsuccessful laboratories were not using recommended screening methods, that they lacked experience in testing for these diseases, and that rationalisation of such screening services may be indicated.