Use

This test is useful for monitoring the effectiveness of therapy in patients who have hyperphenylalaninemia. Hyperphenylalaninemia is characterized by an increased level of phenylalanine and can be improved with dietary management and, in some cases, additional treatments such as tetrahydrobiopterin supplementation or enzyme replacement therapy. While this test provides critical monitoring for patients receiving therapy, it should not be used as a follow-up to abnormal newborn screenings or for diagnosing the specific cause of hyperphenylalaninemia, like tetrahydrobiopterin deficiency, as it cannot rule out all causes on its own.