Difference between RAST and CAP-RAST??? - Peanut Allergy Information

Difference between RAST and CAP-RAST???

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We saw our pediatric allergist today for the second time today since our now 3.5 year old son was diagnosed with PA at 21 months. Andre was diagnosed with PA by skin prick. I don't have the exact measurement of the wheal, but it was not large at all.

Andre has had absolutely no exposure since then. We took him to the allergist today and asked for a CAP-RAST test so that we could monitor the levels as he gets older. We also wanted him to be tested for tree nuts and sesame seeds, as we are very cautious about cross-contamination with these items, but don't know whether he's actually allergic).

Our allergist told us the CAP-RAST is really just a particular brand of the RAST test, and that not only did he not know of any labs that would run it, but also that our insurance (which is great insurance) would not cover it. He said the RAST was our only option.

We live in Rochester, NY, which has several high quality teaching hospitals. I find it hard to believe there are no labs in our area -- or even out of the area -- where he could have the CAP-RAST done?

I'm just curious what the true difference is between the two tests, and if we'll be lacking vital information because we were only able to have the RAST test done?

We'll have the results in about a week.

Thanks for any insight!

------------------ Susan Andre's Mom

On Mar 5, 2003

Susan, We have only done the prick test on the back all these years but will being demanding the blood work in the next month. My daughters back went crazy. She swelled up a 2x2inch area immediately, within 10 seconds. She has as high as they go for the prick tests. Call your insurance company and ask why you can't get the blood test one. I know they will only do that test for foods with most insurance companies. So that might be a thing to look at. Feel free to contact me whenever. Cindy

On Mar 7, 2003

There IS a difference between rast and cap-rast. The rast test has been around for years, can be used for many,MANY different foods, etc. and has generally been considered an "okay" test. The CAP-RAST (aka Immuno-Cap) test is much newer, has only been developed for a few of the MOST deadly allergies (peanut, shellfish,egg to name a few) and is FAR SUPERIOR to the original rast test.My daughter's pediatrician had not heard of the test when we first asked for it 2 years ago, and neither had the lab technician. They double checked with the lab and what do you know? the patient's mother knew something they didn't! My daughter has had the cap rast twice, at 3 and again at 4. I plan on doing it every year until she's six (if she hasn't outgrown it by then, it's unlikely that she ever will) my daughter's pediatrician now wants to make sure she gets the test also. Our results have been quite interesting, the first test Zelda's score was "off the chart" she was >100, but just one year later it had dropped down to 50-something. I asked Dr. Young (at a presentation he was giving) if he thought that Zelda would be a "resolver" given her background, lowered scores, etc. and he said her scores where still WAY to high, most resolvers have MUCH lower initial scores, BUT he stressed that it was NOT IMPOSSIBLE for her to outgrow the allergy and tracking her with yearly tests until at least age 6 would be prudent. If nothing else, it would be interesting to follow the numbers. We live in the Boston area and have had no trouble getting the test, but I have heard that folks in remote locations might not have access to a lab that performs the cap-rast. I can't imagine that it's not available in New York! Sorry this is so long winded, I feel rather strongly that the Cap Rast is a useful test in monitoring the severity of an allergy. If I had to pay out of pocket for the test-I would. At least once early on to get a 'baseline' and once again at age 6, just to see... hope that helps, Diane

On Mar 7, 2003

By the way, I initially took my daughter to MY allergist for testing, he did the skin prick. When I later asked him for the Cap-rast he said that it was 'unreliable'. I believe that he was refering to the old rast test and I suspect that he had not HEARD of the CAP RAST. He is nearing retirement and I wouldn't be surprised if he just didn't know better. He does not have a lot of pediatric patients or patients with food allergies. He's a good doctor, don't get me wrong, but peanut allergies and all the new studies regarding PA just really don't impact on his particular practice. I still use him for MY allergy issues, but my daughter just goes to her pediatrician now. Her pediatrician is not greatly informed on the issue (doctors have SO much to keep up on) BUT the Doctor is GREAT about responding to EVERYTHING regarding PA that I bring her, and has provided me with everything I've asked for re: testing etc.. Maybe you need a new doctor? Hope this wasn't a bummer, Docs can be rather intimidating and defensive when we claim to know things they don't (and who wouldn't be?) I know, both from experience and from the Doctors in my family. take care, Diane

On Mar 7, 2003

Melrose Mum, thank you so much for the clarification. My daughter had the rast test as an infant and scored as allergic to lots of foods. That test was ordered by her G.I. doc., and our allergist really disregarded the results so we didn't think much more about it. We had the Cap Rast done a little over a year ago and she scored a class 5 or 6 to both peanuts and walnuts, which are the two things we know for sure she is allergic to. I plan to have her Cap Rast tested every two years (for the forseeable future) just to keep an eye on how - or if - her numbers change. I never understood the difference, though. We live near Stanford University and that is the hospital we go to for the Cap Rast. I agree that it should be readily available in the New York area. [img]http://uumor.pair.com/nutalle2/peanutallergy/smile.gif[/img] Miriam

On Mar 7, 2003

Thanks for all the input everyone. I had a feeling our allergist was either not as knowledgeable about CAP-RAST as he should be, or else was not in the mood to "indulge" me if you will. We have decided just to live with the RAST results for now, as the blood draw was pretty traumatic for Andre and we don't want to put him through another at this point. I really wanted the test just so that we could have a baseline level, and then continue to monitor it over the years.

The only reason we took Andre to this allergist is because he treats my husband's environmental allergies. He is board certified in pediatrics as well, although you'd never know it! I did find a pediatric allergist in our area, and I'll be asking our pediatrician for a referral to him in a year. I'll definitely insist on the CAP-RAST at that time.

Again, thanks for the input!

------------------ Susan Andre's Mom

On Oct 23, 2003

My son had a skin test & rast test at 10m then this summer 2yrs he had a cap rast done. I had to wait about 1 1/2 for the results as the lab in my area could not run the test so it was send out of State. I live in the Detroit area

On Oct 23, 2003

My PA ds just had a caprast done, we live in Indiana, and they sent it to the lab at Mayo Clinic. We don't have a problem with our insurance, it pays for everything.

------------------ Tina Trevor 8/6/01 Harmony 1/22/03

By Larry Zemlick on Sep 12, 2011

There are 3 major Specific IgE tests on the market. ImmunoCAP Is the predominant test and is used by the major reference labs and research centers.

Some labs do NOT have ImmunoCAP, and some insurers require that you use a particular lab. So...if your insurer requires you to use a lab that does not offer ImmunoCAP then you might not be able to access it.

Please research the "UKnow Peanut Test". It think you will find it interesting. My company makes this test (we also make ImmunoCAP). I don't want to "sell" anything here, so please research this test for more information - it is a recently FDA approved specialty test for peanut allergy.