There is more to test for than just PKU. www.pediatrix.com
has the most comprehensive screen. The biggest risk is your risk of a infection from the heal poke.
Metabolic disease is much easier to treat if you know early. There is far more damage done than just mental retardation and death. Think total emotional, physical, and financial upheavel.
Keep in mind, we are living in a world where it is not the least bit easy to get a diagnosis of metabolic disease UNLESS your child is dead or in the ICU.
Your child can be the first "affected" individual in a very long family line of no one "affected." Carriers have to have children with other carriers. AND some metabolic diseases happen spotaneously. Your one sister who is very hypoglycemic. Your FIL who has achy legs. Your great great uncle who never seemed quite right. Your grandfather who had no tolerance for alcohol. Your other "allergic" child who has no confirmed allergies.
Some people are not diagnosed with metabolic diseases until they are in their 50s. Most children are diagnosed at their autopsy.
There are about 50 screens, but nearly 1500 metabolic diseases. Still, knowing early saves lives.