Pre-analytic decrease of phenylalanine in plasma of patients with phenylketonuria treated with pegvaliase.

Treatment of phenylketonuria (PKU) has evolved since the initial introduction of a phenylalanine (Phe) restricted diet. The most recent option for adults affected with PKU is treatment with an alternate enzyme, phenylalanine ammonia lyase (PAL), that metabolizes excess Phe. Proper management of all patients with PKU relies on accurate measurement of Phe levels in blood, to comply with guidance intended to minimize the neurological symptoms.

Laboratory monitoring of patients with hereditary tyrosinemia type I.

Background: The prognosis of patients with Hereditary Tyrosinemia Type 1 (HT-1) has greatly improved with early detection through newborn screening and the introduction of nitisinone (NTBC) therapy. A recent guideline calls for periodic monitoring of biochemical markers and NTBC levels to tailor treatment; however, this is currently only achieved through a combination of clinical laboratory tests. We developed a multiplexed assay measuring relevant amino acids, succinylacetone (SUAC), and NTBC in dried blood spots (DBS) to facilitate treatment monitoring.

The critical role of psychosine in screening, diagnosis, and monitoring of Krabbe disease.

Purpose: Newborn screening (NBS) for Krabbe disease (KD) is performed by measurement of galactocerebrosidase (GALC) activity as the primary test. This revealed that GALC activity has poor specificity for KD. Psychosine (PSY) was proposed as a disease marker useful to reduce the false positive rate for NBS and for disease monitoring.