Table 1 Justification and benefits of the neonatal BH₄ loading test

1

BH₄ treatment is now available from birth in Europe (as well as USA)

2

The Phe concentration in the newborn with a genetic defect in phenylalanine metabolism is spontaneously evaluated

3

The neonatal test allows the early diagnosis of GTPCH or PTPS deficiency

4

The normalization of blood Phe concentration will be reached sooner in the responsive neonates

5

The 24-h test only delays the management of the condition by 24 h and allows treatment to begin within the first 10 days of life

6

A complete phenotype of the patient is generated (Phe level and BH₄ responsiveness)

7

The parents are rapidly informed of the types of treatment that are available for their child

8

Some patients will be able to avoid the dietetic treatment from birth

9

The good safety profile of this molecule is well established

10

The neonatal test avoids performing a Phe load in young patients after the newborn period