Use

This test is useful for monitoring the effectiveness of dietary therapy in patients with hyperphenylalaninemia, a condition often caused by defects in phenylalanine hydroxylase (PAH). While it helps in the evaluation of patients with hyperphenylalaninemia or phenylketonuria (PKU), it is not sufficient as a follow-up for abnormal newborn screening results since other causes of HPA, like BH4 deficiency, cannot be excluded. Tyrosinemia type I requires medical management, and this test assists in such scenarios by providing measurements of phenylalanine and tyrosine levels as well as their ratios.