How accurate are the blood tests for food allergies? (2.5yo needs testing)

[Ophelia]

I found out when DS was a newborn that he had a reaction to wheat. I don't know if it is just wheat, or gluten so neither of us ingest gluten.
I'm checking into getting him tested for an allergy first (versus celiac). His primary care doctor can do a blood draw and send it off to the lab.

I'm thinking a blood draw is less invasive than those awful skin prick tests. I've had the skin tests done 3 times, most recently this last summer, and it was very painful for me, I don't want to put him through that if I can help it. He has never had blood drawn other than newborn prick on his foot. I'd also rather do the blood test so we can test for several foods, as I have food allergies (nuts, soy, some beans).

Can they test for lots of different foods other than the usual suspects, like oats, barley, peas, etc?

Are the blood tests usually pretty accurate?

Can you give me your experiences with the blood tests?

Any advice on helping him through the tests when we do have them done?

How do you explain to a 2.5yo what is going to happen w/o freaking him out? He is very good verbally and understands most things. I'm also concerned about him freaking out the next time we take him to the doc after testing, I know he's going to be afraid he'll get poked again.

[Ophelia]

no one here have the allergy blood tests done? or did I just post this at the wrong time?

[deditus]

I'll try to help.
If he hasn't been eating gluten, then a celiac test won't be accurate at all. You need to eat gluten for at least 6 months to have enough damage for the bloodwork to be positive.
To answer the rest, I think we need more info. What are his symptoms?
I assume your PCP is drawing blood to send it in for a RAST test, which only tests for immediate allergies which cause symptoms like hives, trouble breathing, etc, but not behavorial symptoms.

Originally Posted by Ophelia

I found out when DS was a newborn that he had a reaction to wheat. I don't know if it is just wheat, or gluten so neither of us ingest gluten.
I'm checking into getting him tested for an allergy first (versus celiac). His primary care doctor can do a blood draw and send it off to the lab.

I'm thinking a blood draw is less invasive than those awful skin prick tests. I've had the skin tests done 3 times, most recently this last summer, and it was very painful for me, I don't want to put him through that if I can help it. He has never had blood drawn other than newborn prick on his foot. I'd also rather do the blood test so we can test for several foods, as I have food allergies (nuts, soy, some beans).

Can they test for lots of different foods other than the usual suspects, like oats, barley, peas, etc?

Are the blood tests usually pretty accurate?

Can you give me your experiences with the blood tests?

Any advice on helping him through the tests when we do have them done?

How do you explain to a 2.5yo what is going to happen w/o freaking him out? He is very good verbally and understands most things. I'm also concerned about him freaking out the next time we take him to the doc after testing, I know he's going to be afraid he'll get poked again.

[Chinese Pistache]

MY dd was 15 mths when we had both spt and blood tests done. The blood testing was much more invasive and painful. She didn't even blink when they did the spt (just hated sitting still for 10 minutes afterward to see results). The blood tests yielded no results, said everything was neg. The spt showed 2 pos results, but we only had 10 things tested with it. We used those results along with food journaling and elimination diet to figure everything else out.

[Ophelia]

I knew you had to be ingesting gluten in order for it to show up on the celiac tests, I just wasn't sure how long you had to be ingesting it for. 6 months is a long time! I don't really want him to know what he's missing either, that's another problem.

His symptoms: productive toots, mucousy poohs (and poohing a lot), a burn rash on his rectum area that would not go away (irritated skin from mucous), eczema spots, bad cradle cap. All went away 6 days after I cut out wheat from my diet. He was 2 months old. I used to cheat occassionally but then he would get spots again, and I think he's also snuck wheat at daycare and gotten the burn rash. And for a time when he was just over 1yo and eating solids good, daycare 'forgot' about the no wheat, or didn't think fruit loops were made of it, because I only found out she was feeding them to him after he had colors on his shirt :

Chinese Pistache, that makes me a little nervous now I'm not sure what would be better. I found the skin prick tests very painful, maybe everyone just has different pain thresholds. I also know it might be a bit easier to do a quick skin prick, other than having to hold him still for a blood draw. So after thinking about it, maybe I should just make an allergist appt and have them skin test a few things I'm concerned about (wheat plus a few other things I'm allergic to). What do you think?

[mom0810]

Depends on what type of blood test. Immunocap rest is the most sensitive of the blood tests. The old rast is pretty useless, but many dr's still use it.

[isaoma]

I'm not an expert of the subject, but I know that testing a toddler for a food allergy isn't exact (I have a 28 month old dd).

We took my dd to see a ped allergist last spring and he preformed a skin prick test. Although it wasn't painful per se, the itching can be uncomfortable. But, after reading up about skin prick tests, I don' t think I will subject her to them any longer.

Here is an exerpt from Janice Joneja:
"It is well known that many agents can be effectively delivered to the body via the skin. Hormones, vaccines, antitoxins and proteins are efficiently introduced into the body via this route, circumventing the digestive tract and powerfully targeting the effector system for which they are designed. There is no reason to suppose that allergens delivered through the skin by absorption (in a patch), by injection (intradermally) or by pricking or scratching, should not induce allergen-specific IgE in a similar manner. "

and

"I have actively discouraged my patients from having skin tests performed, especially on atopic children, because of the risk of inducing IgE via this route. In good conscience I could never condone any action that might result, in an extreme case, in a life-threatening anaphylactic reaction. Even milder reactions can result in a life-time of misery."

The rest can be found at this website, towards the bottom, section C "Comments from our Editors" in a discussion box:

http://allergyadvisor.com/Educational/April04.htm

[kjbrown92]

From the symptoms, it sounds like it could either be an IgE or an IgG response. So even if you get negative results from an IgE test, he could still have IgG food issues. I had the IgE (SPT) testing done for my two kids for food to rule them out. They were all negative. Then I had ALCAT testing done for both of them for IgG testing. It was expensive and not covered by insurance. There was one false negative for each of them. I don't know about false positives because I took all the foods out that they told me to, and then viola - no more tantrums, crying, waking up all night long, etc. Now it's been 7 months, and I'm starting to trial foods again. I had the IgE testing done on DD when she was 2.5 years old (actually it wasn't SPT, they actually injected the allergen under the skin - intradermal testing), and the ALCAT testing (blood draw) when she was just over 3yo. My DS was older. She did better with the blood draw than the intradermal testing. Probably because that was like 30 needle sticks (10 foods, 3 pricks each).

[Chinese Pistache]

Originally Posted by isaoma

I'm not an expert of the subject, but I know that testing a toddler for a food allergy isn't exact (I have a 28 month old dd).

We took my dd to see a ped allergist last spring and he preformed a skin prick test. Although it wasn't painful per se, the itching can be uncomfortable. But, after reading up about skin prick tests, I don' t think I will subject her to them any longer.

Here is an exerpt from Janice Joneja:
"It is well known that many agents can be effectively delivered to the body via the skin. Hormones, vaccines, antitoxins and proteins are efficiently introduced into the body via this route, circumventing the digestive tract and powerfully targeting the effector system for which they are designed. There is no reason to suppose that allergens delivered through the skin by absorption (in a patch), by injection (intradermally) or by pricking or scratching, should not induce allergen-specific IgE in a similar manner. "

and

"I have actively discouraged my patients from having skin tests performed, especially on atopic children, because of the risk of inducing IgE via this route. In good conscience I could never condone any action that might result, in an extreme case, in a life-threatening anaphylactic reaction. Even milder reactions can result in a life-time of misery."

The rest can be found at this website, towards the bottom, section C "Comments from our Editors" in a discussion box:

http://allergyadvisor.com/Educational/April04.htm

That's a good point. I had no idea about allergies at all when we took dd in. I'm not sure what I would do now. Well, actually, I know what I'm doing for my ds who is showing signs of allergy and that is: food journaling and elimination, and it's working fine so far. Skin is clear, poop is normal, etc.

[Ophelia]

The comment on allergyadvisor is interesting....so is she saying that the SPT can CAUSE an allergy that didn't previously exist, by introducing it through the skin? She doesn't link to any studies.

From the symptoms, it sounds like it could either be an IgE or an IgG response. So even if you get negative results from an IgE test, he could still have IgG food issues.

I'm confused about this part. Is there a website that easily explains the difference between IgE and IgG? I have briefly read about it before but don't remember exactly. Thanks!