Phenylketonuria (PKU), inborn error of metabolism, results from phenylalanine hydroxylase deficiency. PKU leads to neurological manifestations, intellectual disability, and mental disorders. Treatment depends on phenylalanine-restricted diet. Diagnosis and follow-up of PKU depends on blood phenylalanine level. The development of bacterial inhibition assay was the first routine screening test for PKU. ELISA and amino acids analyzers methods were then developed. Tandem mass spectrometry was introduced for newborn screening from dried blood spot in the late 1990s. Since then, several methods were developed, starting from using HPLC column followed by direct injection in mass spectrometer by analyte derivatization and use of external and internal standards. Kits are available for neonatal screening without derivatization using internal standards for quantitation. Due to high PKU incidence in Egypt, it is important to continuously ameliorate the methods for neonatal diagnosis and follow-up. External standards as dried blood spots were prepared according to the previously described procedures. These standards were evaluated for phenylalanine concentration using ELISA kit. Analysis of samples was done with a single-step elution from dried blood spot followed by 1-min mass spectrometry analysis. Validation was done according to US FDA and other related guidelines. Fifty samples were analyzed by ELISA and another 126 samples were analyzed by mass spectrometer kit. All these samples were analyzed by the developed method and no statistically significant difference was observed. New simple method is developed for phenylalanine quantitation in dried blood spot using tandem mass spectrometry. This method is cost and time effective.

中文翻译：

---

开发一种使用串联质谱法分析干血斑中苯丙氨酸的简单方法

苯丙酮尿症 (PKU)，先天性代谢障碍，由苯丙氨酸羟化酶缺乏引起。PKU 会导致神经系统表现、智力障碍和精神障碍。治疗取决于苯丙氨酸限制饮食。PKU 的诊断和随访取决于血苯丙氨酸水平。细菌抑制试验的发展是 PKU 的第一个常规筛选试验。然后开发了 ELISA 和氨基酸分析仪方法。串联质谱法在 1990 年代后期被引入用于新生儿干血斑筛查。从那时起，开发了多种方法，从使用 HPLC 色谱柱开始，然后通过分析物衍生化直接进样到质谱仪中，并使用外标和内标。试剂盒可用于新生儿筛查，无需衍生化，使用内标进行定量。由于埃及 PKU 发病率高，因此不断改进​​新生儿诊断和随访方法非常重要。根据先前描述的程序制备作为干血斑的外标。使用 ELISA 试剂盒评估这些标准品的苯丙氨酸浓度。样品分析是通过从干血斑中一步洗脱然后进行 1 分钟质谱分析来完成的。验证是根据美国 FDA 和其他相关指南进行的。通过ELISA分析了50个样品，通过质谱仪试剂盒分析了另外126个样品。所有这些样品都通过开发的方法进行分析，没有观察到统计学上的显着差异。开发了一种使用串联质谱法对干血斑中苯丙氨酸进行定量的简单新方法。这种方法既经济又省时。