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Monitoring effectiveness of dietary therapy in patients with hyperphenylalaninemia
Phenylketonuria: Evaluation of patients with hyperphenylalaninemia or monitoring effectiveness of dietary therapy. Not sufficient follow-up for abnormal newborn screening results, because other causes of hyperphenylalaninemia (eg, BH4 deficiency) cannot be excluded by this test alone.
Tyrosinemia, type I: For medical management.
Defects in phenylalanine hydroxylase (PAH) cause the majority of cases of hyperphenylalanemia (HPA), however approximately 2% of infants with HPA have impaired synthesis or recycling of tetrahydrobiopterin (BH4).
Measurement of phenylalanine and tyrosine is not sufficient to establish a diagnosis of phenylketonuria (PKU) because other forms of HPA are not excluded by this test.
This test is useful for the follow-up of patients with hyperphenylalaninemia to assess appropriate dietary intake.
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)