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Int. J. Neonatal Screen. 2016, 2(2), 2; https://doi.org/10.3390/ijns2020002

A Rapid and Sensitive UPLC-MS/MS-Method for the Separation and Quantification of Branched-Chain Amino Acids from Dried Blood Samples of Patients with Maple Syrup Urine Disease (MSUD)

1
Swiss Newborn Screening Laboratory, Children’s Research Center, University Children’s Hospital, Steinwiesstr. 75, Zurich CH-8032, Switzerland
2
Laboratory Becker, Olgemöller & Colleagues, Führichstr. 70, Munich D-81671, Germany
3
Departement of Clincal Chemistry and Biochemistry, University Children’s Hospital, Steinwiesstr. 75, Zurich CH-8032, Switzerland
4
Waters AG, Täfernstr. 4, Baden-Dättwil CH-5405, Switzerland
Present address: sourceIN GmbH, Wagistr. 21, Schlieren CH-8952, Switzerland.
*
Author to whom correspondence should be addressed.
Academic Editor: Peter C.J.I. Schielen
Received: 18 March 2016 / Revised: 10 May 2016 / Accepted: 27 May 2016 / Published: 2 June 2016
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Abstract

Newborn screening for MSUD is a special challenge since patients with MSUD can metabolically decompensate rapidly without adequate treatment within the first two weeks of life. However, the screening method does not detect the actual marker metabolite (alloisoleucine) specifically, but only as part of the group of the other isobaric amino acids leucine, isoleucine and hydroxyproline. We describe a sensitive and rapid second-tier UPLC-MS/MS method to determine branched-chain amino acids from the initial extraction of the screening sample. Quantification is based on a seven-point calibration curve. Reference ranges (mean ± SD in µmol/L) were determined from 179 normal, not pre-selected samples from the newborn screening: leucine: 72 ± 27; isoleucine: 37 ± 19; valine: 98 ± 46; hydroxyproline: 23 ± 13. The concentration of alloisoleucine was below the detection limit in about 55% of the cases, and the highest concentration was 1.9 µmol/L. In all 30 retrospectively studied screening samples from patients with confirmed MSUD the concentration of alloisoleucine was significantly increased. In 238 samples with false-positive newborn screening due to a significant increase in the combined concentration of leucine + isoleucine + alloisoleucine + hydroxyproline (400 to >4000 µmol/L), alloisoleucine was below 6.5 µmol/L (n = 57) or not detectable (n = 181). The application of this assay markedly reduces the false-positive rate and the associated anxiety and costs. It is also suitable for routinely monitoring blood spots of patients with MSUD. View Full-Text
Keywords: newborn screening; neonatal screening; maple syrup urine disease; MSUD; dried blood spots; patient follow up; inborn errors of metabolism; IEM newborn screening; neonatal screening; maple syrup urine disease; MSUD; dried blood spots; patient follow up; inborn errors of metabolism; IEM
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Fingerhut, R.; Röschinger, W.; Heck, M. A Rapid and Sensitive UPLC-MS/MS-Method for the Separation and Quantification of Branched-Chain Amino Acids from Dried Blood Samples of Patients with Maple Syrup Urine Disease (MSUD). Int. J. Neonatal Screen. 2016, 2, 2.

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