Testing for Allergies

Posted on: Thu, 06/01/2006 - 7:24am
antree's picture
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Joined: 05/23/2006 - 09:00

I keep reading about RAST test, which I think is a blood test, Right?
If it is the blood test, it seems everyone has had one. My son has only had the scratch test, is there a difference? He has been tested twice, once at 16mos when we found out about the PA and EA he out grew the egg allergy at 2 1/2. And the 2nd time at 2 1/2 after he was hospitalized for eating a Peanut Butter Cup. He will get tested again July 2007 before school starts to see if he out grew the PA. His 2nd scratch test showed the hive was large then
his first scratch test. So would that say the allergy is getting worst. Should he have a blood test?

Thanks Maria

Posted on: Thu, 06/01/2006 - 7:59am
luvmyboys's picture
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Joined: 05/25/2006 - 09:00

I am not well versed on comparing scratch tests but I can tell you a little about the RAST. Many here prefer the RAST because there is no chance of exposure or reaction from the test itself, allowing you to retest year to year with no concern. There is a chance of false negative with the RAST so if negative, should be followed by a scratch test if you have reason to believe there is an allergy. Scratch has more chance of a false positive (usually because of sensitive skin and/or nurse slipping with the needle???) Anyhow, that is why we chose RAST...we already knew ds was allergic so why chance the prick? Another thing to note...recent exposure to the allergen will increase RAST numbers for a couple of weeks. Good luck!
luvmyboys

Posted on: Thu, 06/01/2006 - 9:37am
Daisy's picture
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Joined: 01/16/2006 - 09:00

I am an adult with food allergies. I was officially diagnosed in my thirties by SPT. This is the standard method of testing. My allergist did not use the RAST, as the skin testing was sufficient for my allergies at the time.
The RAST test can be a good method for [b]tracking allergies through the years[/b] or confirming weak or questionable SPT results.(You really do not want to keep *exposing* your child to the peanut un-necessarily with yearly SPT.) That is why some Docs will do the RAST, instead, for follow-up visits. Then, if this is negative, the Doc will do the SPT. Then, and only then, if that is also negative, an oral challenge may be done. (I would only do this in a hospital-type setting. Very scary!)
Am I getting this right...your son was dx'd at 16mos w/ SPT? Then, your Doc did the SPT again at 2 1/2? WHY? Didn't you already know he was PA?
Daisy

Posted on: Thu, 06/01/2006 - 9:53am
smudgesgarden's picture
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Joined: 02/26/2006 - 09:00

my son has only had the scratch test.
our allergy dr has never sugested the rast test.
before we have a food challenge test i think i will have a rast test done, but for now i dont think there is a need for it. (and i dont think id have a food challenge test with peanuts any ways. to scarry)
also the hive being bigger than the first time just means they held the needle difrently. the first time my son was tested for allergys he tested neg. for peanuts. the second time (after a reaction with a pbj danwitch)he had a huge reaction to peanuts, hive larger than a silver dollar, the third test the hive was the size of a pea, but his allergy is more severe than when it was first diagnosed...
-----
erin

Posted on: Thu, 06/01/2006 - 1:32pm
antree's picture
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Joined: 05/23/2006 - 09:00

Hi Daisy, the reason we had another test done was because we asked for it. I quess you can say we were still in denial. He was hospitalized at the end of May because of exposure and when we went to the allergist in July, I was just hoping he had out grown it and the dr saw how upset I was, he agreed to do the test. We really didn't know anything about this allergy, and I had and still have a lot to learn.
Maria

Posted on: Thu, 06/01/2006 - 1:39pm
Daisy's picture
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Joined: 01/16/2006 - 09:00

Antree,
Of course you are still learning. That is where your Doc should have stepped in. This would have been a perfect reason for the RAST...to comfort Mom.
Ask for the RAST, instead of the SPT at the 2007 appt. And keep a copy for your records.
Daisy

Posted on: Thu, 06/01/2006 - 7:59am
luvmyboys's picture
Offline
Joined: 05/25/2006 - 09:00

I am not well versed on comparing scratch tests but I can tell you a little about the RAST. Many here prefer the RAST because there is no chance of exposure or reaction from the test itself, allowing you to retest year to year with no concern. There is a chance of false negative with the RAST so if negative, should be followed by a scratch test if you have reason to believe there is an allergy. Scratch has more chance of a false positive (usually because of sensitive skin and/or nurse slipping with the needle???) Anyhow, that is why we chose RAST...we already knew ds was allergic so why chance the prick? Another thing to note...recent exposure to the allergen will increase RAST numbers for a couple of weeks. Good luck!
luvmyboys

Posted on: Thu, 06/01/2006 - 9:37am
Daisy's picture
Offline
Joined: 01/16/2006 - 09:00

I am an adult with food allergies. I was officially diagnosed in my thirties by SPT. This is the standard method of testing. My allergist did not use the RAST, as the skin testing was sufficient for my allergies at the time.
The RAST test can be a good method for [b]tracking allergies through the years[/b] or confirming weak or questionable SPT results.(You really do not want to keep *exposing* your child to the peanut un-necessarily with yearly SPT.) That is why some Docs will do the RAST, instead, for follow-up visits. Then, if this is negative, the Doc will do the SPT. Then, and only then, if that is also negative, an oral challenge may be done. (I would only do this in a hospital-type setting. Very scary!)
Am I getting this right...your son was dx'd at 16mos w/ SPT? Then, your Doc did the SPT again at 2 1/2? WHY? Didn't you already know he was PA?
Daisy

Posted on: Thu, 06/01/2006 - 9:53am
smudgesgarden's picture
Offline
Joined: 02/26/2006 - 09:00

my son has only had the scratch test.
our allergy dr has never sugested the rast test.
before we have a food challenge test i think i will have a rast test done, but for now i dont think there is a need for it. (and i dont think id have a food challenge test with peanuts any ways. to scarry)
also the hive being bigger than the first time just means they held the needle difrently. the first time my son was tested for allergys he tested neg. for peanuts. the second time (after a reaction with a pbj danwitch)he had a huge reaction to peanuts, hive larger than a silver dollar, the third test the hive was the size of a pea, but his allergy is more severe than when it was first diagnosed...
-----
erin

Posted on: Thu, 06/01/2006 - 1:32pm
antree's picture
Offline
Joined: 05/23/2006 - 09:00

Hi Daisy, the reason we had another test done was because we asked for it. I quess you can say we were still in denial. He was hospitalized at the end of May because of exposure and when we went to the allergist in July, I was just hoping he had out grown it and the dr saw how upset I was, he agreed to do the test. We really didn't know anything about this allergy, and I had and still have a lot to learn.
Maria

Posted on: Thu, 06/01/2006 - 1:39pm
Daisy's picture
Offline
Joined: 01/16/2006 - 09:00

Antree,
Of course you are still learning. That is where your Doc should have stepped in. This would have been a perfect reason for the RAST...to comfort Mom.
Ask for the RAST, instead of the SPT at the 2007 appt. And keep a copy for your records.
Daisy

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