The state health department notifies a nursery staff nurse of a phenylketonuria (pku) metabolic screening test result of [7 mg/dl (423.5 mcmol/l)] for a neonate discharged several days ago. what should the nursery nurse do

The answer to this question would be: Immediately notify the physician because the test result is critically elevated.
Phenylketonuria is a disease that was caused by lack of the enzyme to digest phenylalanine so the metabolic waste can be accumulated. The disease can cause permanent growth reta.rdation to the patient.  But early treatment can prevent the damage. That is why the physician should inform the parent immediately.