Talking Allergies

Does anyone know what the range is? Or have a link to something that explains what your number might mean?

Saskmommyof2,
Did you ever find an answer for this? I've been looking and can't seem to find anything. I got the test results from my daughter's RAST test yesterday. The nurse explained that it's a scale of 1 to 6, 1 being low and anything from 3-6 is considered high. My daughter got a 5 for peanut. I was just looking for a more detail explanation of what a 5 is.

She was low for eggs so as long as we don't feed her raw eggs she's fine.

I am not sure if there are different ways to score the test but my daughter had a 10 for peanut and 12 for milk last year. We were told that these were in a high range. My husband found a link last summer but I forget what it was. I will ask him to find it again.

I heard that they can go really high...like up to 100 or so. My friends daughter scored 38.5 for peanut which was considered quite high. They will do a food challenge if <0.35. Other than that I do not know a lot, we have not had a RAST yet. We are scheduled for my oldest daughter to have one next fall, and I would like to know what the result really means. Hope someone else can add some more info on this.

I think the on the 1-6 scale the numbers fall into a range...I think 38.5 was in the range of about a 4 or 5.

When the RAST test is done, there are 2 different ways of scoring. Both methods are used for each individual. The first score is on a scale of 0-100 kU/L. This number is used to determine where you sit with the second score of 0-6. For example, if a you scored 55kU/L for peanuts, that would sit you with a RAST score of 5, which means there is a very high level of allergen specific IgE (RAST). My allergist has said that any score over 10 ( in the scoring from 0-100) places you at anaphylactic risk. Hope this helps.

This is the scale, as described on the copy of a friend's RAST(my friend photocopied it for me to show to our allergist because she could not remember the name of the test) :

<0.35 KU/L : ALLERGEN LEVEL 0 - ABSENT OR UNDETECTABLE ALLERGEN SPECIFIC IgE

0.35 - 0.69 : ALLERGEN LEVEL 1 - LOW OF ALLERGEN SPECIFIC IgE

0.70 - 3.49 : ALLERGEN LEVEL 2 - MODERATE LEVEL OF ALLERGEN SPECIFIC IgE

3.50 - 17.49 : ALLERGEN LEVEL 3 - HIGH LEVEL OF ALLERGEN SPECIFIC IgE

17.50 - 49.99 : ALLERGEN LEVEL 4 - VERY HIGH LEVEL OF ALLERGEN SPECIFIC IgE

50.0 - 100.00 : ALLERGEN LEVEL 5 - VERY HIGH LEVEL OF ALLERGEN SPECIFIC IgE

> 100.00 : ALLERGEN LEVEL 6 - EXTREMELY HIGH LEVEL OF ALLERGEN SPECIFIC IgE

The result sheet also had the following statement:

IN FOOD ALLERGY, CIRCULATING IgE ANTIBODIES MAY REMAIN UNDETECTABLE BECAUSE THE ANTIBODY MAY BE DIRECTED TO ALLERGENS THAT ARE REVEALED OR ALTERED DURING INDUSTRIAL PROCESSING, COOKING OR DIGESTION AND DO NOT EXIST IN THE ORIGINAL FOOD.

A NEGATIVE OR EQUIVOCAL TEST RESULT SHOULD NOT BE INTERPRETED TO MEAN THAT THE PATIENT IS NOT OR NO LONGER SENSITIVE TO THE ALLERGEN TESTED. HYPERSENSITIVITY REACTIONS MAY STILL OCCUR. RESULTS SHOULD BE INTERPRETED WITH CAUTION.

Thanks, Nicole. That's really helpful. I've only had one RAST test....I'm class II for wheat apparently.

Just to add, the RAST doesn't indicate a level of allergic reaction, it just measures the number of IgE antibodies that the body produces. There are false positives and false negatives. You could have a high level of antibodies and not have an allergic response as well as no antibodies and have an allergic response.

Not very helpful am I....

I think I'm really confused now....so, the RAST isn't a predictor of the severity of an allergic reaction, but does it accurately reflect the presence of an allergy? What do you mean -- false positives and false negatives with the RAST?

From what I gather,allergists don't just rely on one test, because of the risk of false positives and negatives with both the skin tests and the RASTS. Rather, they try to "create a picture" consisting of history of previous reactions, skin test and RAST results combined.

We are going to see the dr. next Wednesday to get the results of my daughter's RAST, as the skin test was inconclusive (a very tiny wheal for peanuts). I will ask her about the percentage level of false negatives and positives.

From what I have researched and learned from our allergist, Nicole has it right. RAST does not indicate severity of allergic reaction. It can give an indication of what someone is allergic to, but it isn't 100% accurate. I don't know the actual statistic for accuracy. The test doesn't stand alone though and our allergist would not feel an food allergy was conclusive without further evidence. I think environmental allergiies are more accurate with RAST.

Our youngest had a RAST for a whole bunch of things when his eczema was really bad and I was restricting my diet as I was breastfeeding. The pediatrician thought it would help give a picture of what was happening and hopefully "free up" my diet. The allergist didn't find the information terribly helpful as he says the only true test for food allergy is to try it and see what happens (within reason of course depending on history etc etc).

We've been introducing solids and potato caused a definite eczema flare up. The allergist requested a RAST to confirm it. The level of IgE measured was 99 which is very high. He was not anaphylactic, but had an obvious reaction. Someone else might not show anything or have a more severe reaction to a lower number.

does that help?

Yes, thanks -- in my son's case, he had a reaction to actually ingesting peanut. He had a large wheel with his SPT at the allergist's office and his RAST score was also very high. His allergist explained that he wanted the RAST to determine IgE levels over time to guage the possibility of his ever outgrowing it (although not too promising given all of his tests). Have you also heard that there is a correlation between a high RAST and lifelong allergy?

We saw our allergisit in June and got recent RAST results for some of my son's allergies... the Dr. reported the numbers to be "low", a Class 1 I guess, and he did say that this was a good sign he may grow out of some of these allergies! So it sounded to me like low numbers (or numbers trending downwards) could suggest the possibility of outgrowing allergies.
As k-rae said, our allergist told us that around the age of 4, it would be a good idea to food challenge our son (especially to things he has never reacted to - or been exposed to only through breastmilk).. the only true way to know for sure. I am sure hoping for some false negatives in there!!

I haven't heard of that correlation....is that coming from you allergist? To be honest, I have to hope it isn't true, as the number of things that tested very high for my poor babe is ridiculous.

I find it all confusing as I've read that in adults, complete avoidance of the food for several years can lead to the IgE levels returning to 0...therefore not being allergic to the food anymore. Last week in a discussion with our allergist, he said that there are studies in children (I think with peanut - not anaphylactic) that continued exposure to the allergen actually increased the chances of outgrowing it. Somehow desensitizing the immune system to not recognize the food as bad. Seems conflicting, but I'm no clinical immunologist!!

Yes, it was the allergist who said low numbers were reason to be hopeful. But, I have read many examples on another allergy site about people with high RAST scores, which decline over time, so don't despair!
Regarding the exposures.. I have heard that too. Our allergist also said that as long as the numbers stayed low, we may try very slowly introducing some things (ie. a drop of milk a day, increasing by a drop a day, to see if he can "build a tolerance"). Of course I assume too that this is only for people with very low scores and proabably a negative food challenge too.
Does it ever worry you that we are doing the wrong thing by avoiding all these foods while pregnant and bf'ing... and delaying the introduction of foods for so long (especially the allergenic ones)? Some recent things I have heard are sugesting this (like k-rae said). Although I guess the vast majority of research still supports avoidance and delay. Hmmm...
I'm not doubting that strict avoidance would result in decreasing IgE levels, but when I was a child (maybe 7ish), I was SPT pos for peanuts, strawberries, chocolate and tomatos.. . I remember getting a red face with hives from eating these things. Allergy knowledge being what it was then... I didn't stop eating any of these things! I don't know when it happened, but I definitely outgrew these allergies. So, I suspect that different people resond differently to avoidance/exposure etc.