Research for the newborn screening system by tandem mass spectrometry

为了改善日本遗传性代谢紊乱患者的预后和生活质量，研究了串联质谱法（TMS）作为新生儿筛查的新方法的有效性。在新生儿出生后第5天或第6天，在父母知情同意的情况下，在福井、广岛和德岛县以及其他地区的选定医院采集血样。我们开发了一种微孔板进样工艺，通过使用自动进样器的TMS仪器每年可测量100，000份样品。我们分析了81，000名新生儿，发现4名丙酸血症患者和1名II型瓜氨酸血症患者。所有丙酸血症患者在限制蛋白质饮食和给予肉毒碱治疗下均生长良好，并对有机酸代谢紊乱、脂肪酸氧化紊乱、肉毒碱循环紊乱和尿素循环紊乱患者的新生儿血斑进行了分析。丙酰肉毒碱与乙酰肉毒碱的比值是鉴别轻度丙酸血症和甲基丙二酸血症患者的敏感指标。在新生儿血斑有症状的患者脂肪酸氧化障碍，包括中链酰基辅酶A脱氢酶缺乏症，酰基肉毒碱配置文件为进一步的诊断研究提供信息。瓜氨酸血症患者的瓜氨酸水平高于1，000 nmol/ml，而严重的鸟氨酸转氨甲酰酶缺乏症患者的瓜氨酸水平低于6 nmol/ml。根据本研究结果，在日本TMS新生儿筛查中，患有目标疾病的患者的频率被认为超过1至20，000名新生儿。我们认为，应建立全国性的TMS新生儿筛查系统。

The usefulness of tandem mass spectometry (TMS) as a new method for newborn screening was investigated in order to improve the prognosis and quality of life of the patients with inherited metabolic disorders in Japan. The blood samples were collected on the fifth or sixth day of life of the newborns, with the informed consent of their parents, in the prefectures of Fukui, Hiroshima and Tokushima, and from selected hospitals in the other areas. We developed a microplate sample process for the measurement of 100,000 samples per year by one TMS instrument using an autoinjector. We analyzed 81,000 newborns and found 4 patients with propionic acidemia and one patient with type II citrullinemia. All of the patients with propionic acidemia are growing uneventfully under the therapies of a protein-restricted diet and carnitine administration.We also analyzed the newborn blood spot s of the patients with such disorders as organic acidemias, disorders of fatty acid oxidation, disorders in carnitine cycle, and disorders in urea cycle. The ratio of propionylcarnitine to acetylcarnitine were shown to be a sensitive marker to identify patients with mild form of propionic acidemia and methylmalonic acidemia. In newborn blood spots of symptomatic patients with fatty acid oxidation disorders, including medium-chai acylCoA dehydrogenase deficiency, acylcarnitine profiles were informative for further diagnostic studies. Citrulline levels were heigher than 1,000 nmo/ml in patients with citrullinemia and lower than 6 nmol/ml in patients with severe forms of ornithine transcarbamylase deficiency.Based on the results in this study, the frequency of the patients with the target disorders in TMS newborn screening in Japan is thought to be more than 1 to 20,000 newborns. We belieave that the nation-wide system of TMS newborn screening should be developed.