Jensen U G, Brandt N J, Christensen E, Skovby F, Nørgaard-Pedersen B, Simonsen H
Department of Clinical Biochemistry, Statens Serum Institut, 5 Artillerivej, DK-2300 Copenhagen S, Denmark.
Clin Chem. 2001 Aug;47(8):1364-72.
Classic galactosemia (OMIM 230400) is an inherited disorder in the metabolism of galactose caused by deficiency of the enzyme galactose 1-phosphate uridyl transferase (EC 2.7.7.12). Galactosemia leads to accumulation of galactose and galactose 1-phosphate (gal-1-P) in blood and tissues and, if untreated, produces neonatal death or severe mental retardation, cirrhosis of the liver, and cataracts. Hence, the disorder is included in many neonatal screening programs.
We retrospectively analyzed filter-paper blood samples obtained 4-8 days postpartum for routine neonatal screening from 12 galactosemia patients and 2055 random controls. Total hexose monophosphates (HMPs) were used as a marker of gal-1-P and were assayed by negative-ion mode electrospray tandem mass spectrometry (tandem MS) with settings biased toward gal-1-P detection. The predominant precursor/product ion pair m/z 259/79 was used to quantify total HMPs by external standardization.
Linear calibration curves were obtained in the range 0-8 mmol/L gal-1-P. The detection limit was 0.1 mmol/L HMP, and total CVs ranged from 13% at the detection limit to <8% at >1 mmol/L HMP. The method was in agreement with an alkaline phosphatase-galactose dehydrogenase method. All samples from galactosemia patients contained increased HMP concentrations (range for patients, 2.6-5.2 mmol/L; range for reference group, <0.10-0.94 mmol/L). The diagnostic sensitivity and specificity were 100% at a cutoff of 1.2 mmol/L HMP. A Duarte/classic galactosemia compound heterozygous sample could be discriminated clearly from both patient and reference samples.
Quantitative analysis of HMPs by tandem MS can be used in laboratory investigations of galactosemia.
经典型半乳糖血症（OMIM 230400）是一种由于缺乏1-磷酸半乳糖尿苷转移酶（EC 2.7.7.12）而导致的半乳糖代谢遗传性疾病。半乳糖血症会导致血液和组织中半乳糖及1-磷酸半乳糖（gal-1-P）蓄积，若不治疗，会导致新生儿死亡或严重智力发育迟缓、肝硬化及白内障。因此，该疾病被纳入许多新生儿筛查项目。
我们回顾性分析了12例半乳糖血症患者和2055例随机对照的产后4 - 8天用于常规新生儿筛查的滤纸血样。总己糖单磷酸酯（HMPs）用作gal-1-P的标志物，采用负离子模式电喷雾串联质谱法（串联质谱）进行检测，其设置偏向于gal-1-P的检测。主要的前体/产物离子对m/z 259/79用于通过外标法对总HMPs进行定量。
在0 - 8 mmol/L gal-1-P范围内获得了线性校准曲线。检测限为0.1 mmol/L HMP，总变异系数范围从检测限处的13%到>1 mmol/L HMP时的<8%。该方法与碱性磷酸酶 - 半乳糖脱氢酶法一致。所有半乳糖血症患者的样本中HMP浓度均升高（患者范围为2.6 - 5.2 mmol/L；参考组范围为<0.10 - 0.94 mmol/L）。在HMP截断值为1.2 mmol/L时，诊断敏感性和特异性均为100%。可以将杜氏/经典型半乳糖血症复合杂合子样本与患者样本和参考样本清楚地区分开。
串联质谱法对HMPs进行定量分析可用于半乳糖血症的实验室研究。
