Ummmm.... not all cf patients are really skinny (or even have digestive symptoms or pancreatic insufficiency, esp early on), just like not all cf patients present with lung issues (some have digestive issues early on and no respiratory symptoms!) I believe you mentioned in another post, though, that he's only in the 5-10th% for growth, and if ht and wt match percentiles, of course he won't look 'skinny.' However, to be so small for his age IS of concern.
The pediatrician is not an expert in CF. He has too many concerning symptoms to let go and if she tries to deny this testing, make her put it in writing in his chart that you have asked for the genetic testing due to his culturing pseudomonas and having multiple other symptoms of concern and that she is denying it and whatever her reason for denying it is. There are many people with CF that have normal sweat tests.
I would seek a 2nd opinion if the ped is not cooperative. I would also look into what your insurance requires when it comes to seeing specialists. If you are able to get to a CF center without the ped sending you there, I would strongly suggest doing so. If possible, call an accredited CF center, ask to talk to the nurse (not just the scheduling secretary), explain both what is going on with your son as well as how the ped has handled it, and see what they say.
Wishing the very best. <img src="i/expressions/rose.gif" border="0">