hi! i wasn't aware your son was being tested. my best friend's daughter has pdd. how old is your son, close to joe's age i think... never mind, i see 3.5.
can i ask why he is being tested? to what degree does the pdd affect his life? does he speak at all?
i think you should explain it to your son if he seems like he wants to know what is going on. most parents prob. wouldn't even consider a 3 yo might have questions- good for you, i have always thought from your posts that you seem like a very good mama to your boy.
my friend's daughter has pdd pretty severe, she is nonverbal, but can follow instructions, she understands SO much. when she was born her parents were told to just leave her be, because she was a "vegatable" who would never think or feel.
of course her parents have SHOWERED her w/love & she is now able to give & show affection.
so, my best advice is, don't listed to the drs. listen to your son & your gut. autism/pdd is so different from child to child that the drs. really don't know what to do in a lot of cases.
i forget where you live- nevada?! pm me if you want, if you have more questions. my friend would be glad to talk to you if you want to hear from a mom who has been there. her dd is almost six.
good luck to you, give your son a hug from me!