Both RAST and skin prick tests have similar rates of false positives.  Neither of them is overly accurate.  Some allergists prefer one test over the other, but most I know use skin prick testing first because it gives results within 15 minutes, versus several hours (or even days) for RAST testing.  Some allergists like to correlate both tests when an allergy is particularly difficult to diagnose, or if someone has sensitive skin that welts up easily from skin pricks, making it more difficult to read. 

If you are avoiding something with no reaction history to tat food, your allergist's office may even be able to book a food challenge after the skin prick test, so it is all done on the same day if the skin prick is negative. 

Agreed, Space, and that was my fault having our ped write the previous order.  However, my question is, given the inaccuracy of the that test (I never knew there was that high of a percentage of false positives), I'm wondering if it is even worth testing the things we are concerned about!?  Or maybe instead of RAST doing skinprick instead would be beneficial?

Your allergist should only order RAST testing for the foods you are concerned about. That way, you don't get a bunch of meaningless numbers for foods you know are well tolerated.

Hi, Everyone!

So, it's been a few years since my PN/Sesame allergic daughter has been tested, and we recently went to the allergist who suggested doing RAST testing.  On the one hand, I would like to see if her numbers for PN/Sesame have changed, or perhaps look at the numbers of things we have avoided (like TN/Shellfish) and maybe consider a challenge (we are going on a major trip abroad this summer and knowing that perhaps TN/Shellfish were safe for her would not necessarily see her consuming them, but see me not as uptight about the possibility of CC). 

HOWEVER, last time she did a RAST panel test (including environmental) she had a TON of false positives.  This, along with the prohibitively expensive cost, is making me reconsider, despite the peace of mind it *may* give me.  Ironically, when we did that test, some things that we avoid (TN/Shellfish) came back boarderline (class 0/1) and things like corn, soy, milk and wheat, which she eats on a regular basis, came back class 1/2!  Anyone have any thoughts on reliability of RAST tests and whether or not they are worth the headache?

Thanks!