in canada all kids are tested with the heel prick. There is a about 17% rate of error in the test b/c they want to make sure they do not miss someone so they set their limits very low. People who are carriers of pku (but do not have it) usually have higher levels of phe in their body and it is possible he is just a carrier. the average person has about 40-60 at any given point but those who are carriers have higher. Those who have pku are ususally defined as those whose numbers are over 360. A second blood test is needed and then they also do a urine catch. These tests go to london ontario (the only place in canada as far as i know) to be tested for bh4 defficientcy among other things. This test takes about 6 weeks to get back. In the meantime you will likely be treated for pku. The goal in canada is to keep your numbers (or in this case your son's numbers) between 120 and 360. If- untreated his numbers are naturally at this range then you will be told to introduce him to a small amount of specialized formula (but likely not until he is out of the hospital). My doctor says that this is b/c he may need it later on and the taste is so horrid that they have to introduce it as babies or else the kids won't take it. The formula also has tyr supplimentation. You will learn his TYR numbers whenever they do a phe test b/c they also need to be in range (higher than 50 is ideal) so aid in brain development.
PKU is a bit of a catchall term- there are different forms of pku and a genetic test will tell you quicly what kind you have but it is not readily available b/c the type of pku doesn't really matter as they are all treated the same. Diet is managed to ensure the numbers are in range. If they have bioptrin deficiency rather than true pku then he'll just need a little pill every day but will still be tested to make sure his numbers stay in range!!