When preparing to obtain a neonatal screening test for phenylketonuria (PKU), the neonate must have received which of the following to ensure reliable results? 1. A feeding of an iron-rich formula. 2....

When preparing to obtain a neonatal screening test for phenylketonuria (PKU), the neonate must have received which of the following to ensure reliable results?

1. A feeding of an iron-rich formula.

2. Nothing by mouth for 4 hours before the test.

3. Initial formula or breast milk at least 24 hours before the test.

4. A feeding of glucose water.