A Simple and Rapid Method Based on Liquid Chromatography–Tandem Mass Spectrometry for the Measurement of α-L-Iduronidase Activity in Dried Blood Spots: An Application to Mucopolysaccharidosis I (Hurler) Screening

• Published in: Annals of laboratory medicine Vol. 35; no. 1; pp. 41 - 49
• Main Authors: Yang, Jeong Soo, Min, Hye Kyeong, Oh, Hyeon Ju, Woo, Hye In, Lee, Soo-Youn, Kim, Jong-Won, Song, Junghan, Park, Hyung-Doo
• Format: Journal Article
• Language: English
• Published: Korea (South) The Korean Society for Laboratory Medicine 01.01.2015; 대한진단검사의학회
• Subjects: Chromatography, High Pressure Liquid; Dried Blood Spot Testing - instrumentation; Humans; Iduronidase - analysis; Iduronidase - metabolism; Mucopolysaccharidosis I - blood; Mucopolysaccharidosis I - diagnosis; Original; Regression Analysis; Substrate Specificity; Tandem Mass Spectrometry; 병리학; Mucopolysaccharidosis I; Mass spectrometry; Iduronidase
• ISSN: 2234-3806; 2234-3814; 2234-3814
• DOI: 10.3343/alm.2015.35.1.41

We developed an analytical method to measure α-L-iduronidase (IDUA) activity in dried blood spots. This was achieved by using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) with electrospray ionization in the positive ion mode. Chromatographic separation was completed using mobile phase involving water-formic acid and acetonitrile-formic acid over 2.8 min of run time on a column with a Kinetex XB-C18 (Phenomenex, USA). The detection of column effluent was performed using a Xevo TQ-S triple quadrupole mass spectrometer (Waters, USA) in the multiple-reaction monitoring mode. This method was verified with blank and control samples at four activity levels: base, low, medium, and high. Control materials were provided from Centers for Disease Control and Prevention (CDC). Intra- and inter-day precisions were between 2.6% and 16.5% and between 7.9% and 17.0%, respectively. A correlative regression study on the IDUA activity in CDC-control samples performed to assess the validity of the developed method showed a highly significant linear association (r(2)=0.9976) between the calculated and CDC-reported values and an obvious difference in activity among the four levels. This reliable analytical method was applied to mucopolysaccharidosis I (Hurler) screening of patients under treatment (n=4) and in normal controls (n=129). IDUA activity ranged from 8.98 to 77.12 µmol/hr/L) in normal controls, and patients undergoing medical treatment showed low IDUA activity. This method had advantages of simplicity, rapid sample preparation, and liquid chromatographic separation, which efficiently inhibited ionization suppression induced by matrix effects in mass spectrometric detection.