do the RAST scores really mean anything?

Posted on: Sat, 05/22/2004 - 11:14pm
lalow's picture
Joined: 03/24/2004 - 09:00

I have been reading so much on here and have started to wonder if the RAST scores mean a whole lot. MY son scored low on all the things he scored positive for. Class 1 for peanut, soy, egg and banana and Class 2 for milk. I am not sure the soy, egg and banana are really positive as I have seen no reaction to them, but we are to avoid them for a while anyway. I keep telling myself that the low scores are good. However, the allergist stressed when he gave me the scores that his reactions to milk and peanut are life threatening and not to take it lightly even with a class 1 and 2. So do these scores not indicate severity? Do they atleast mean he is more likely to outgrow the allergies?

Posted on: Sun, 05/23/2004 - 9:48am
BENSMOM's picture
Joined: 05/20/2000 - 09:00

The scores supposedly indicate the likelihood of a reaction and the amount needed to cause a reaction. So a low score would mean he might react to a decent amount of peanut. My son is a fluke. His RAST score is over 100--off the charts. He's never reacted and had plenty of contact with cross-contaminated items, eating items with peanut flour, and eating food where he simply picked off the peanuts. He even tasted pb before he was diagnosed with no reaction.
Here's some new research that I recently read. I'm wondering if this could explain my son. I don't really understand it, but it sounds like there are different peanut proteins, or different "things" in peanut for something to bond to? Like I said, I don't really understand it, but I may take my son back to Dr. Wood to look into it.
In the July 2003 issue of the J Allergy Clin Immunology Beyer et al had a publication (which should have been posted much earlier) entitled Measurement of peptide-specific IgE as an additional tool in identifying patients with clinical reactivity to peanuts. As the authors note in the abstract of the article,"Diagnostic decision levels of food-specific IgE antibody concentrations have been described" (as seen in the above postings). "However, many patients still need to undergo oral peanut challenges because their IgE levels are in the nondiagnostic level".The aim of their study was to determine whether differences exist in IgE-binding epitope recognition between sensitized children with and without symptomatic peanut allergy. Eight peptides representing the immunodominant sequential epitopes on Ara h 1, 2, and 3 were synthesized ... Individual patient labeling was performed with sera from 15 patients with symptomatic peanut allergy and 16 patients who were sensitized but tolerant. Ten of these 16 patients had "outgrown" their allergy.
Regardless of their peanut-specific IgE levels, most patients with symptomatic peanut allergy showed IgE binding to the 3 immunodominant epitopes on Ara h 2.
In contrast, each of these epitopes was recognized by < 10% of the tolerant patients.
In addition, tolerant patients did not recognize 2 immunodominant epitopes on Ara h 1.
At least 93% of symptomatic, but only 12.5% of tolerant patients, recognized 1 of these "predictive" epitopes on Ara h 1 or 2.
Moreover, the cumulative IgE binding to the peanut peptides was significantly higher in patients with peanut allergy than in tolerant patients.
With up to 50% of patients with peanut-specific IgE levels below diagnostic decision levels still being clinically reactive, oral food challenges could be avoided in ~90% of these patients through determination of peptide-specific IgE.
CONCLUSIONS: Determination of epitope recognition provides an additional tool to diagnose symptomatic peanut allergy, especially in children with peanut-specific IgE below diagnostic decision levels. (posted only March 14th, 2004)214
Here's a link. You can also go to the links section of It's the "where do we stand" article.
This testing is supposed to be for borderline cases, but Dr. Wood was quite surprised with Ben's test results, considering his lack of reaction history. He's tested over 100 twice, so it wasn't a mistake.
Sorry to get off your question a bit. The RAST score won't tell you the severity of a reaction, but a low test score may indicate a little less sensitivity.

Posted on: Sun, 05/23/2004 - 1:01pm
Naer74's picture
Joined: 11/03/2003 - 09:00

My PA son's situation is the exact opposite of Bensmom. My son's RAST score was negative. The allergist told us it was zero. However, he did still test positive to cashews (negative skin prick but did have anaphylactic reaction to) and pistachios.
So they set up a food challenge. He reacted within 30 seconds of him having a dime size amount in his mouth that he spit out. He had hives, full body redness, gagging, and excessive saliva or drool. The only difference in this reaction and his previous ones is that he did not exhibit the coughing/asthma attacks nor the vomitting/diarrhea. He also reacted a month later with swelling and coughing.
What Bensmom said about it possibly indicating a less sensitivity with low test scores does not hold true to my son...he even reacted to cross contamination with pudding. I am not saying this isn't true...I don't have a medical degree.
I just find the whole skin test/RAST test scores sooooo confusing.

Posted on: Sun, 05/23/2004 - 1:10pm
Nicole1401's picture
Joined: 12/27/2002 - 09:00

Quote:Originally posted by lalow:
[b]However, the allergist stressed when he gave me the scores that his reactions to milk and peanut are life threatening and not to take it lightly even with a class 1 and 2. [/b]
My dd is getting tested Tuesday for a milk allergy. Do you know why the dr said to consider your son's milk allergy life threatening? I understand that peanut allergies should all be treated as if they are life threatening. But, I also thought I understood that to not be true for milk allergies. How do drs determine whether or not someone with a milk allergy needs an epipen and how do parents determine how careful to be in regards to allowing their milk-allergic child to be around dairy products?
I know that this is taking the thread off-topic. I am sorry about that. If I could answer your question about RAST scores, I certainly would. But, I am extremely confused about their worth right now.

Posted on: Sun, 05/23/2004 - 2:10pm
lalow's picture
Joined: 03/24/2004 - 09:00

O.K. to answer the question about what my allergist said about the potential of milk allergies to be life threatening. I am assuming he was stating that because allergies to milk have the potential to being anaphalatic. My son's most severe reaction have been hives, facial swelling, and eczema. However, I believe he said to becarefull because he has reacted to very small amounts of milk products (like he broke out in hives from eating a piece of bread from a sandwich that had cheese on it. He didnt eat any of the cheese though). I think he gave us the epi-pen because of his peanut allergy.. not the milk. I am very confused about it all.

Posted on: Sun, 05/23/2004 - 11:47pm
Nicole1401's picture
Joined: 12/27/2002 - 09:00

Thank you lalow. I truly believe that our allergist doesn't have a clue when it comes to food allergies. We've tried several and settled on this one because so far he has been willing to do what I ask for. Therefore, I have to gather as much info as I can in order to know what to ask for (which tests, epi Rx, etc). It is frustrating!

Posted on: Mon, 05/24/2004 - 9:09am
ks65's picture
Joined: 03/06/2002 - 09:00

milk can be life-threatening. My almost 3 yr old son has a life threatening milk allergy. When he was 15 months, milk spilled on him and he got hives wherever it touched. He touched his eye and it swelled shut for a day. We carry an Epi. He shows thru the CAP RAST and skin prick to be allergic to egg, wheat and peanuts...although to our knowledge he has never had peanuts. My 5 yr old daughter is PA we have the Epi's and would use them on either child if needed too. I think any allergy has the potential to be life-threatening..every person's reactions/history is different.

Posted on: Tue, 05/25/2004 - 3:17pm
Driving Me Nutty's picture
Joined: 05/01/2003 - 09:00

Quote:Originally posted by lalow:
[b]So do these scores not indicate severity? Do they atleast mean he is more likely to outgrow the allergies?[/b]
From what I learned at the FAAN conference, RAST scores indicate the [b]likelihood[/b] of a reaction, [b]not[/b] the severity of a reaction. I have heard of stories of anaphyactic reactions when the score was 1 and 2.
From what I've read, the lower the score, the better the chance the person has of outgrowing the allergy. My dd is class 6 as it was >100, so unfortunately she has very little chance of outgrowing it.
[This message has been edited by Driving Me Nutty (edited May 26, 2004).]

Posted on: Wed, 05/26/2004 - 9:01am
mommyofmatt's picture
Joined: 03/12/2004 - 09:00

Continuing on the milk topic (sorry lalow), my neighbor's son chugged a cup of milk and went into anaphylactic shock, so it does happen w/milk.
My ds took 1 small sip and got hives, started itching his ears, coughing and crying. If I hadn't gotten to him in time, I think he would have been very sick, and his milk is only class 1 now according to latest test results. So be as careful as you can w/milk.
Meg, mom to:
Matt 2 yrs. PA,MA,EA
Sean 2 yrs. NKA

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