False Positives?

Posted on: Thu, 02/01/2007 - 4:57am
KateDe's picture
Joined: 09/20/2006 - 09:00

"There are no doubt parents of children who hang out on this board who have false-positive readings and whose kids aren't really allergic."

That's a quote from BrianandBrina's mom on the thread I started about that FAAN article and it's basically what the article said. What I am asking is how is that possible? I am holding out hope that my son is a false positive, although it's safe to say because he got many hives from just being surrounded by peanuts that his results aren't false. However, how would I know? Shy of giving him something with peanuts, which I'd never do, how would I know that his allergy results are false positives? How often does this happen?

Are there parents out there that are living in fear when they don't have to be?

Posted on: Thu, 02/01/2007 - 5:22am
Corvallis Mom's picture
Joined: 05/22/2001 - 09:00

I think that the answer to your question is a resounding YES.
Clinical reactivity trumps test results. Period.
How is this possible? Well-- nobody knows for certain what relationship IgE has to actual reactivity. Skin tests are notoriously BAD predictors of food allergy reactivity. They are reasonably good at negative prediction-- so a negative skin test is accurate something like 80-95% of the time... but positive results are only about 50-50.
So someone [i]could[/i] be tested for peanuts without any indication that they are allergic and come back with high IgE levels and a huge skin test. Are they truly allergic?
Most researchers would say "Probably, but maybe not." At a certain IgE level, though, peanut reactivity is almost guaranteed. So no allergist that I know of would [i]dare[/i] conduct an oral challenge on a child with no history of ingestion OR reactivity, but an IgE topping 100 kU/L.
I wish that there were a way to evaluate the allergy more accurately without risk. Not just because the not-really-allergic can get away with things (like bakery items and gross cross-contamination) that we can't, but also because they shouldn't have to live with fear of something that isn't a problem for them.

Posted on: Thu, 02/01/2007 - 5:27am
chanda4's picture
Joined: 12/14/2006 - 09:00

I think I can understand both sides of this. I'm not sure if my kids have had false positives or not.....here are a few examples....
My daughter Sidney, who just turned 8 was recently tested for a bunch of allergens. I took her in for asthma, but the allergist went ahead and tested her. To my knowledge she didn't have any food allergies(my only one). To our surprise beef and chocolate came back positive. And even the doctor noted it could be a *false positive* and to pay attention to any reactions. She's 8.....she's been eating beef and chocolate for years! One evening recently, she ate a whopper Jr and a chocolate milk. Within 15min she felt really icky, got a migraine and even got body aches(flu-like is how I describe it).....so, is it really a false positive or is she allergic?? I really have no idea! For now I've told her no more beef or chocolate and we'd try again ina few months.
another example....my son is allergic to soy so they say). Until he was age 2, soy would always show negative on his skin and blood tests. But everytime he'd eat soy yogurt, he'd have diarrhea the next couple days. After age 2, they retested him and it was positive in the blood work and slightly on the skin. Now at age 3, retested him recently and it was negative again(both tests)....so again I don't know if it was a false positive or not, but since he gets diarrhea, I keep it out of his diet.
So, to me, I can undertsand why some people may say thier child is allergic, tests may say they are, btu they really don't have reactions(not like you would if you ate a pb&j).....what is difficult with all this is that allergies can be minor and allergies can be deadly.............and for most of us(with milk, egg, nuts) you DON'T KNOW!!!! And that is what scares the crud out of me. My daughter was positive to beef, but if she eats it nothing serious happens. My 3yr old is alelrgic to milk, btu there's noooo way I'd give him a glass to see what his reaction is.
There is such a wide spectrum of reactions, that there is no way possible to know who is over-exagerating or who really could die. We just have to RESPECT everyone who is allergic, who might be allergic or who might be making it all up.....because it's a dangerous game trying to figure out otherwise.
edit....ps I know only one of my kids is peanut/nut allergic, but I value this site and the opinions here. So I hope I can stay too, even though only 1 of the 4 is nut allergic....the info shared here helps me with ALL my kids food allergies.
Chanda(mother of 4)
Savannah-1 (milk and egg)
[This message has been edited by chanda4 (edited February 01, 2007).]

Posted on: Thu, 02/01/2007 - 5:32am
KaraLH's picture
Joined: 10/11/2006 - 09:00

This is very interesting to me because of my DD test results. She test positive, but we had never really connected any of her reactions to peanuts. Her first allergist said, "yep, she's allergic, she can't have any more peanuts, no may contains and no processed on equipment or in shared facility stuff." My DH and I were thrown. It has made us question every reaction she has ever had. We kept on asking "could it have been from peanuts?" Usually it didn't seem likely. The best we could tell was perhaps more of a GI reaction from peanuts. Seems more rare, yet it can happen.
Then we saw a new allergist 2 weeks ago. He felt that without a strong clinical history of a reaction from peanuts the test may have been false-positive. However, he did say that with her history of allergies (many other confirmed FA's) she may have built up a sensitivity to peanuts and therefore we should not give her any peanuts or peanut containing products for at least two years. Then we can revisit it. He did say she was probably safe to eat "processed on or in a facility with" items.
That is great for her- and for us. My question is if we become vey lax on what we give her now, could we contribute to forming a true peanut allergy? As far as I can tell everyone has an opinion and no one really knows for sure.
I think we will go with our new allergists advice for now.
Maybe someone else here has insight on my DD's situation.
In light of all of this, I hope know one minds if I stick around even if my daughter doesn't have a true peanut allergy. I have learned so much here and want to continue learning more.

Posted on: Thu, 02/01/2007 - 5:36am
Anonymous's picture
Anonymous (not verified)

Wow. Okay.
My son has had false positives on a skin prick test to things OTHER than peanut, but on the peanut part of the spt, which I wouldn't allow to even be scratched, the wheal was quite large just from the serum being placed on his skin.
If I even remotely thought that my child was a false positive PA, I wouldn't be hanging around here - I'd be getting some answers.
My son has had three anaphylactic reactions (I am not uttering that proudly) and a few others along the way. He's PA.
Now as far as whatever strange TROUT he tested positive to, no, that was a false positive. [img]http://uumor.pair.com/nutalle2/peanutallergy/biggrin.gif[/img]
There but for the Grace of God, go I.

Posted on: Thu, 02/01/2007 - 5:43am
melissiabeth's picture
Joined: 05/24/2006 - 09:00

My daughter has been diagnoised peanut allergic through testing only. We went to the allergist because of her ezcema- she was tested for 25 things. Her only positive was peanuts. Her skin test produced a strong positive (15mm) we were given epi pens and sent on our way.
On the advice of my pediatrician we went to a second allergist who does RAST testing and is a pediatric allergist- he and the nurse actually made a horrible face when I told them that my daughter has never had a reaction and just tested allergic. He said that blind allergy testing is unreliabe and the only way to accurately diagnois an allergy is through reaction.
My daughter has had some exposure to peanuts before her positive testing- mostly through may contains but actually did eat 1/4 of a peanut butter cracker my neice accidently gave her and some ice cream that the peanuts were just picked off. She has never had a known reaction. Her RAST was .82 and if it stays under a 2, the allergist will give her a food challenge at 5.
So either we've been given a wonderful gift and we know to avoid peanuts hardcore and are prepared with epi pens if something accidently happens or we've been screwed into living this way (in fear) for no reason.
If she does pass a food challenge one day- I wouldn't say she outgrew-- I would say she was never allergic.
[This message has been edited by melissiabeth (edited February 01, 2007).]

Posted on: Thu, 02/01/2007 - 5:50am
KateDe's picture
Joined: 09/20/2006 - 09:00

Kara, I've been going through the same struggles as you.
Here's our story. My son had peanut butter at 18 months. Got hives. Had him tested. Blood test was low. Doc said not to worry and that it "would take him a whole bag of peanuts to have an anaphalatic response". I spent a year not worrying. I didn't give him peanuts but I didn't worry about food labels.
A year passed. I had him retested per the allergist's suggestion. Bloodwork level was lower. Great! But I told the allergist how my son got hives from going to a restaurant with peanuts on the floor. Doctor skin tested him in the office and he got a huge welt. I was told not to even think about letting him around peanuts, carry an epi and read everything. I went to another allergist and he said that is good advice and that we could retest in a year.
So now I am living in fear. I am thinking that by not being careful for the past year I have made his allergy worse. Or that it's really not a bad allergy and the results were false.
My son has a couple of mystery hives over the past year or so but I never made the connection to peanuts, except for once. So since the skin test I have been avoiding things that may contain peanuts with him.

Posted on: Thu, 02/01/2007 - 6:58am
Sarahb's picture
Joined: 01/22/2007 - 09:00

My son reacted twice to peanut butter and then was tested and was positive to SPT 30/50. I asked why not test him for everything right now. Our allergist said that would drive me insane and there are many false positives.
She said we would test in the future if there a reaction or reason to test to confirm suspicions not to cast a wide net and see what we find.
I haven't decided if I am going to ask for more tests yet. For now I am adjusting to PA and am prepared for a reaction.

Posted on: Thu, 02/01/2007 - 8:00am
bonestable's picture
Joined: 04/05/2005 - 09:00

I am hoping my DD doesn't actually have a peanut allergy, but for now, I treat her as though she does.
She had an anaphalactic reaction to milk at 7 months, and has also had facial swelling after kiwifruit. Other than that she has had various hives and rashes which we have never been able to pin down for sure.
She has had 4 positive RASTs to peanuts - the highest was 2.89 and the lowest was 0.49, but they go up and down. Maybe when she is 5 we will do a skin test and a food challenge, if the RAST is still low.
Similarly we treat her as allergic to sesame, although this is based on RAST tests only.
She recently had positive RASTs for wheat and soy, which she eats with no problems, so I am confident that these were false positives. But it makes me question the other positives more!
However, we know for sure she is allergic to dairy, so while we are having to be diligent about avoiding milk, it is not too much more effort to avoid peanuts and sesame.
So I could be wrong when I tell people she is allergic to peanuts, and request appropriate precautions. But what else can I do? I refuse to do a food challenge when she is still so young. If she passes a food challenge when she is 5 I will never know if she outgrew it or if she was never allergic.

Posted on: Thu, 02/01/2007 - 8:52am
Momcat's picture
Joined: 03/15/2005 - 09:00

For all those who are wondering...
I don't think peanut allergy is a requirement for membership here at PA.com. You are all welcome to hang out here and get information on peanut allergies whether you or your kids have false positives, true allergies, undiagnosed allergies, etc. We have had members in the past who were not allergic and just wanted to get info and participate in discussions.
Mom to 7 yr old PA/TNA daughter and 4 yr old son who is allergic to eggs.

Posted on: Thu, 02/01/2007 - 9:12am
chanda4's picture
Joined: 12/14/2006 - 09:00

thank you...
I also wanted to point out. Some of us, with siblings, may be protecting younger siblings from a possible peanut allergy. I know I am. So far....Jake's little 3yr old brother has been negative to peanut and all the tree nuts, but I treat him(and my youngest) as if they were positive..... my allergist said to(because of MFA's)....
So I guess in a sense I am treating 2 of my kids as if they were allergic. I don't freak out as bad if someone near them is eating it, but I distance them...just incase. They don't eat any *may containes* or even *made in a facility*.....until they reach age 5 and we can test further, I have to pretend they are.
And it's all because big brother is.
Just something to think about [img]http://uumor.pair.com/nutalle2/peanutallergy/smile.gif[/img]
edit...I got to thinking about this more. My two youngest have also tested high for eggs, but I've never seen a reaction from them. I have however seen a reaction from their positive brother, Jake (his throat squeezes)...so I take their *positive* very serious(because of siblings) even with little *proof*
Chanda(mother of 4)
Savannah-1 (milk and egg)

Posted on: Thu, 02/01/2007 - 9:28am
mommamia8's picture
Joined: 11/13/2005 - 09:00

I am in the same boat. DS is 3 and was tested at 22 months due to a hive reaction from eggs. He turned up positive to a bunch of stuff, including peanut. I have never knowingly given him peanut so I don't know if he would actually react to it. His initial number was 7 something and the latest RAST was 4.2. He had low numbers to milk, soy, some treenuts, etc. etc. Some of these (not treenuts) he had eaten everyday. The allergist recommended NOT to stop with these foods if no reactions.
Then there is the good ole egg. He had egg maybe 4 times before the full body hive episode (first 3 times got hive around the mouth only). So yeah, I KNOW he is allergic to egg. Egg is his highest RAST at 52 and the only "positive" test result confirmed by ingestion. I even had 2 diff. allergist tell me he might not be allergic to peanut, etc.
Anyhoo, the thing I have been thinking about lately is his high total IgE #. Slightly over 500. That means a lot of IgE is circulating in his little body. Why? All our numbers don't add up to 500. I feel like the IgE is just WAITING for something to attack. So I am feeling that STRICT AVOIDANCE to the positive things he has never had isthe answer for our situation. Having had egg 4 times seems to have kicked up his number. Maybe to the point it won't go back down???

Posted on: Thu, 02/01/2007 - 11:43am
lalow's picture
Joined: 03/24/2004 - 09:00

I think if a child has never had a reaction and is young but has tested positive on RAST or skin you have to just treat them as if they are allergic. Sometimes they arent and you will learn that eventually. I know with ds when he was given a RAST at 15 m he tested positive for peanut (class 2), milk, egg, banana and soy. He was not allegic to egg or banana and that we knew cause he never had a reaction and ate them all the time. Soy we discovered made his eczema worse and milk we knew from experience. I was never totally convinced about peanut cause the day he reacted when he ate a piece of pb cookie he picked up he also had a cheese cracker within a few minutes. So i always hoped it was the cheese. Just recently turned 4 he was retested with a skin test. He was positive for milk and peanut (they didnt test the others) and his peanut was stongly pos. (20/50) The dr. didnt question it at all but basically told me she would not retest him for atleast 3 years. But what is good and also difficult is he has had no reactions of anykind to anything in atleast a year. We are better at watching him, he is getting more responsible but in my mind I also think (since he has never had a really bad reaction) maybe they are wrong. But in reality i dont think they are.
James 5 yrs, NKA
Ben 4 yrs, PA and MA

Peanut Free Store

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