My 4.5-month old baby has PKU, so I have learned a lot about the screening test and can provide a little info. The PKU test tests for an error in the body's metabolizing protein, regardless of the source. The test doesn't require that the child have eaten - simply that it has been out of the womb long enough for them to start metabolizing something, be it breast milk, formula or stored fat and their own protein. You in fact never get the results unless there is a problem. Tests over 24 hours should be accurate (but not before, as a recent tragic CA case shows). If there were anything wrong in your screening panel, you would have a re-test. FOr example, my exclusively breast fed baby was tested at about 36 hours, and his blood phenylalanine levels were already many times the norm. He was retested a few days later and the diagnosis was confirmed. So it sounds like everything was done according to procedure, and because untreated metabolic disorders create *devastating* results, sounds like you are lucky.

Lucy & Ryan 5/30/03