Confused about RAST results

Author:
Updated:
Original:

My son had another RAST test done and his allergist says it came back negative. I was elated until I heard the numbers. Last year the results were:

Peanuts - 85% REF Peanut Class - 1 CLASS Peanuts Conc. - <0.35 KU/L Peanut Conc. Class - 0 CLASS

This year the results were:

Peanuts - 68% REF Peanuts Class - 1 CLASS Peanuts Conc. - <0.35 KU/L Peanut Conc. Class - 0 CLASS

The only difference I can see is the 68% REF versus the 85% REF from last year. Does anyone know what this means? I thought that a RAST test isn't negative until the class shows up as 0.

All that being said, however, his allergist strongly recommended that he continue to stay away from all peanut products and continue to carry his epi. He said that RAST tests are not 100% accurate. He didn't think it was a good idea to do the skin test or oral challenge because of exposure issues and the riskiness of it.

Anyways, if there is anyone out there who can clarify this for me, I would greatly appreciate it. I'm not sure if I should be really excited or not. Thanks in advance!

On Mar 28, 2003

First- [img]http://uumor.pair.com/nutalle2/peanutallergy/smile.gif[/img] This is great news, no doubt about [i]that[/i]!!

Has your child had any reactions in the past couple of years? (I would ask why the allergist feels it is too risky to skin test if the answer is no)

I say this because I think this may give you real trouble with schools and the like if they want to know about severity, etc. (You won't have a good answer, I think) Your allergist is right about one thing- this RAST result is so inconclusive that you don't really have any information that is useful... The reason for the difference and sameness of the result is that the RAST, like most tests, has what is called a "linear range" in which results can be determined with pretty good confidence... the trouble is that your child's results for two years now have been below this... so they can't tell you what the actual concentration of IgE is- it's too low to be accurate. (Same thing for kids who are class 6 like my DD- measurement on the test is too high to be in the accurate range of the test.)

This is FABULOUS news for you!!! Kudos for keeping your child away from pn so successfully! [img]http://uumor.pair.com/nutalle2/peanutallergy/smile.gif[/img] Good luck getting up the courage to test eventually, though [img]http://uumor.pair.com/nutalle2/peanutallergy/wink.gif[/img]

On Mar 28, 2003

My son had his first RAST test this fall. I'm looking at my printout of the results, and realize I don't understand all the numbers.

For Peanut (F13) IGE = 65.3 which I think is in the "Equivocal" range

The nurse told me his result was negative for peanut allergy and to go ahead and give him a PB sandwich to test it. @@

Needless to say, I didn't. I took him to an allergist who did a skin test. The peanut scratch welted up immediately and was larger than the control positive.

The allergist said he was definitely allergic. So I am not sure what the value of the RAST test is....

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

On Mar 31, 2003

Hi Corvallis Mom and Jean! Thanks for your replies. I was away this weekend, so I wasn't able to reply sooner.

Jean: How frustrating is that that a nurse in the allergy department would (1) give you the wrong result and (2) give you such horrible advice as to go ahead and give your child PB? Thank God you are smarter than him/her and decided to confirm it with the allergist.

Corvallis Mom: In answer to your questions, my son has not had any reactions to peanut products in the past couple of years. However, last year he reacted (we think) to miso soup which is a soy (lips were a little swollen and red). The weird thing is that the RAST last year showed that he isn't allergic to soy. He didn't eat anything else that he could react to that we know of. As for why the allergist didn't want to do the skin test - basically, he said that it would be an exposure issue. If DS is truly negative, the exposure could possibly bring the allergy back. If the test is wrong and he is actually positive, we could be ruining his chances of outgrowing it. Ditto for the food challenge. He said that a negative result doesn't mean anyone should go out and start eating PB or any peanut products since there are cases of the allergy coming back. He recommends that we continue to live our lives the way we always have and continue to carry the Epi. I guess the only reason why anyone would want to know if they are negative or not is just for peace of mind in knowing that there is a much slighter chance of not having a life threatening reaction to peanut products?

[This message has been edited by Suz-a-loo (edited March 31, 2003).]

[This message has been edited by Suz-a-loo (edited March 31, 2003).]

On Apr 7, 2003

Hello - I was looking at my 15 month old son't RAST test results. He has never ingested peanuts - his ASM percent is 539 - Level 3 from what I read. He has ingested sesame via Hummus - (sesame paste/chick pea mixture) on 3 separate occasions and had hives on face and itchy eyes - his score for sesame was 312 percent - Level 3 also. Of course the allergest told us to use the Epipen Jr/Benadryl if he has a reaction and to stay away from the allergens. Now I am trying to deal with what to safely feed my son and how to have him safely play and be a child - I am home now but will eventually have to look to day care of some sort. This is scary!!!

On Apr 7, 2003

Janro - I am so sorry to hear about your son's test results. I know how frustrating that can be. Although he may have never been exposed to actual peanuts, I know that chick peas are part of the same family as peanuts - legumes. We kept my son away from all legumes since he was diagnosed with his PA. I don't know if that helped make his levels go down. There is hope, though. As you may already know, apparently 20% of children "outgrow" this allergy and my son was considered severely allergic when he was first diagnosed and now he is five and his levels are almost at negative. I put quotes around the word outgrow because I'm not sure that is the correct word to use since his allergist said that exposure could bring the allergy back. Thus, he would have to stay away from all peanut products for the rest of his life. I wish you the best of luck with your son's future testing.

On Apr 7, 2003

Suz- thanks for the reply - unfortunately today was not a good day - we had a reaction to bread crumbs on some eggplant parm I made last night and fed Evan for lunch. The bread crumbs had sesame seeds. He had a couple of hives and I used Benadryl..didn't get to an Epipen situation - hives went away and Evan is fine...can you really ever get a grip on this or do we live the rest of our lives in a bubble and paranoid?

On Apr 8, 2003

Janro - I feel your frustration. It's frustrating to fix meals because we have to scrutinize everything. Then to top it off, we have to research every food company because not all of them are good about labeling practices. Hopefully, that will change sometime soon. Hang in there and keep coming to this site. There is a huge support system here and I know it has helped me many times when I was starting to feel overwhelmed with this whole thing.

On Apr 9, 2003

Hi, you said your sons numbers to pn was high now they are 1. You said you kept your son away from the products.

That's what I'm trying to do but my son's number's are still off the charts. I know every child and situation is different. My son hasn't had a reaction since the 1st time. That was about 9.5 years ago. (Eating it).

The only beans he eats is Brocks chili beans and Campbell Soup(bean and bacon) he hasn't had a reaction to them. I keep thinking I'm doing something wrong and that's why his number's aren't coming down. Do you have any advice?

I'm not sure about your question, though. I've always heard once allergic always allergic. But it does sound like he is outgrowing it. When the test was done and he was so high, did he just have a reaction. I've read somewhere (here maybe) that if you get testing done real soon after an exposure your numbers will be higher. Hope this helps,rj.

[This message has been edited by rj (edited April 09, 2003).]

On Apr 9, 2003

RJ - I think you are right when you said "once allergic, always allergic". It seems that even if a PA person tests negative, they should continue on with life as if they are positive. It appears that the allergy can and does come back. Sorry to hear that your child's levels have not come down. Here we think we are doing the right thing by keeping our kids away from the allergen and still the levels don't come down in some kids. It's all very confusing. But, even if the levels do come down, it doesn't seem to matter because that person still has to stay away from peanuts. I don't know if we are going to bother with testing anymore because it won't change the way we are living our lives.

On Apr 9, 2003

Does it depend on how high or low your rast scores are on whether they can outgrow the allergy or not? I know as far as reactions, it doesn't make a difference.

On Apr 10, 2003

Michele - there is a post entitled " Rast Score? How to read them?" that talks about the scores and chances of outgrowing it. Hope this helps.

Related