Rast Score? How to read them? - Peanut Allergy Information

Rast Score? How to read them?

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My son's allergist basically tells me nothing. Which tells me it's time to find a new allergist. Anyway . . .

My son had the RAST test done, not the CAP RAST. Everyone seems to talk about the Cap Rast. Is it better?

My son's Rast scores were:

Peanut 1.07 KU/L Wheat 3.19 KU/L

What does this mean???


On May 12, 2002

My allergist said: 4-being severely allergic (not likely to outgrow allergy) 3-2% change of outgrowning 2-75% change of outgrowing it 1-80% change of outgrowing it. If your son is a 1 you are so lucky! BUT if you read my other post they also say there are negative positives! Scarey. As far as I know the CAP-RAST test is more accurate. It measures to what degree the child is allergic. So if you want to have him tested in 2 yrs, it will tell if he is outgrowing it our not. In my case my son tested 22.3 KU/L.!! So I don't need a CAP test. I know it is severe, but in you case if might be different. Good luck! Sandy

On May 12, 2002


Originally posted by Sandy: [b]My allergist said: 4-being severely allergic (not likely to outgrow allergy) 3-2% change of outgrowning 2-75% change of outgrowing it 1-80% change of outgrowing it. If your son is a 1 you are so lucky[/b]

I think perhaps you misunderstood the original poster -- her son's test score wasn't a Class 1, but a measurement of 1.07 KU/L. (I assume your allergist was talking about classes, not raw test results when he gave you those figures, since all the scores of 1.something through 4.something KU/L translate to the same class.)

If I recall correctly (and this is simply from memory, so could definitely be off), the original poster's son's score of 1.07 KU/L would be a Class III, which is on the low end of "moderate". (I believe class III starts at .69 or .70 KU/L)

Do you know where your allergist got those numbers about the possibility of outgrowing the allergy? I haven't seen them before, and they seem so optimistic, I'd love to see them from the source before I get my hopes up too much. Thanks.

On May 12, 2002

Hi Lisa~This guide to interpretation of rast levels was on my daughter's test results:

< 0.35 KIU/L antibody absent or at undetectable level 0.35 to 0.78 KIU/L antibody level low 0.71 to 3.50 KIU/L antibody level moderate 3.51 to 17.5 KIU/L antibody level high > 17.5 KIU/L antibody level very high

Allergen-specific IGE interpretation of results: class 0 - <70% class 1 - 70-109% class 2 - 110-219% class 3 - 220-599% class 4 - 600-1999% class 5 - 2000-5999% class 6 - >5999% My daughter's peanut allergy results said: abnormal 14.5 KIU/L ASM rast class 4 1905%

On May 13, 2002

Thank you all so much for your help. I know that it's all the same . . . my son is allergic to peanuts. But, for some reason, understanding the numbers provides some comfort. I appreciate your time and thoughtfulness. Lisa

On Apr 10, 2003

More Confusion (re:RAST test)

Hi again...I recently told my story about me GP ordering a RAST that I later found out was negative, but I was still referredd to a Pediatric allergist and found out Logan was PA and was given Rx for 2 epi's. I was reading all the posts on numbers and class etc listed on Rast tests...SO, to make a long story short, I called to ask if my son's RAST was just neg or if there were numbers involved....First, they just said neg, he can have peanuts....now she said she reviewed his RAST test and he was neg. to eggs, fish, milk and had a Ige of 1...and the scale was from 0-10...so he's in the normal range and can have peanuts...so I told her about his allergist appt, and that he was allergic....had epi's etc. He had his first reaction...lips swelling and hives to just touching the PB lid) at 18 months. I dont know why I cant let this go...the RAST results drive me insane....Is it because it's all knew to me...or am I in denial....a part of me keeps saying, he's really not allergic...then the other part says....he is. The RAST results make no sense to me ....a 1...in a 0-10 range? yet he reacts...can anyone explain or share a similar experience....I'm sticking to what the allergist says....but that darn RAST test haunts me.... Thanks again, Lisa

On Apr 10, 2003

I had to post again to say I'm not a bone-head....and I realize my last posts is full of spelling errors....for that, I apoligize. Lisa

On Apr 10, 2003

Hi Lisa! The way I understand it from our allergist is that even if the test comes back negative, we should continue living our lives as if the allergy is still there. Apparently, there is a good chance that the allergy could come back due to exposure. My son's RAST results were confusing too. There are two different test results. One shows that he is positive and the other shows that he is negative. However, the positive result is extremely low. I, personally, don't see why we should bother with testing anymore since even if it comes back completely negative, we have to live our lives the way we always have anyways. If my son's levels had come back very high, then I think I would want to continue testing him in the future only to see if the levels come down. From what I understand, the lower the levels the less the chance of having a reaction. However, it doesn't lessen the severity of the reaction - just the chance the reaction can happen. So, since there is still the possibility that he can have an anaphylactic reaction, we're just going to stay away from peanuts forever. Hope this helps.

On Apr 10, 2003

My son's RAST test came back negative for peanuts. So they did a scratch test, and he was definitely allergic to peanuts. SO I don't know what value the RAST test really is....

------------------ Jean mom to 3-year-old with PA

On Apr 11, 2003

And what kind of scale is this? Meaning 1-10? 1-5? I am confused now, my allergist told me that if he could place a RAST test on a scale of 1-10, he would place Aidan at a 5.

On Apr 16, 2003

I have a copy of my daughters results from Mayo Clinic. She is a class 3 at 13.4 ku/l

results say (positive 3.51 - 17.5)

Unfortunately this is all the information it gives.