Original
When a baby is born, doctors take a blood sample from their Achilles' heel. They test the sample for various diseases, one of the is PKU. In my country every person with PKU had a close relationship since then with a psychologist, a nutritionist and of course an endocrinologist. In order to keep track of the phe levels in a person, each month a blood sample is sent to the hospital in charge and they analyze it to report back to the family for the progress of the child.