blood tests for allergies

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damo123
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Date Joined Jul 2007
Total Posts : 709
   Posted 8/4/2008 3:31 AM (GMT -7)   
I was wondering how accurate blood tests are to determine food allergies / intolerances. Are the results always to be trusted or can there be false positives and false negatives?
 
I got a blood test done from an allergist to determine if I had food allergies / intolerances. It showed I was severly dairy intolerant and wheat intolerant. But when I told this to my doctor he said he didn't place too much emphasis on the test.
 
I'm a bit confused? Any comments would be great!
 
Thanks,
 
D
 
Med free for a bit as I needed a break from Asacol
 
Probiotics
 
"Whatever you do in life don't berate yourself too much nor contragulate yourself too much. Your choices are half chance. So are everybody elses'"
 
 
 
 
 
 
 


Red_34
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Date Joined Apr 2004
Total Posts : 23424
   Posted 8/4/2008 3:56 AM (GMT -7)   
No test is 100% fail proof. The RAST is pretty accurate when it comes to allergy tests but it can still show false positives and false negatives. But if you have avoided wheat and dairy and it is making you feel better then I would say that the test was true.


 @--->--SHERRY--<---@
Moderator for Allergies/Asthma and Co-moderator for UC
~Left sided Uc-'92-Colazal(9 daily),6mp(50-100mgs),Prilosec,Biotin,Forvia,Pro-Bio**Unable to tolerate Asacol, Rowasa or Canasa**~Year-round allergies-Singulair, Allegra~Secondary Reynauds Syndrome-'04-Norvasc~Spinal Stenosis(?)~Sacroiliitis-epidural injections~bulging and herniated discs C5/C6 & C6/C7~2nd epidural injection 8/14, Neurontin and Skelaxin
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Razzle
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Date Joined Aug 2007
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   Posted 8/4/2008 5:02 AM (GMT -7)   
RAST IgE tests only show allergies, not intolerances. Can have false positives or negatives. And they're not very accurate for food allergies, from what I understand. Supposedly don't have to be actively eating the food for it to show up positive, but some find their IgE levels drop over time if they aren't exposed at least once in a while to the food. That said, my husband has high IgE to many foods, and it has been like this for him for a long time (seems his IgE count doesn't decrease over time so much)...so it may be different for everyone.

IgG ELISA blood tests show delayed reactivity (sensitivity reactions, some call them intolerances), but again, they can miss a lot or can have false positives. And some labs only look at IgG subclass 4 antibodies to foods, whereas there's another lab I was tested through that was considered positive if any of the 4 IgG subclasses showed a response (thought to be more accurate somehow...I just think of it as more comprehensive).
Caveate: patient must have eaten the foods tested within the previous few months to get any sort of accurate result, otherwise results may have false negatives.

ALCAT tests look at any immune response to foods (immedate or delayed allergy/intolerance) and are thought by some to be the most accurate. But like any test, it can have false positives or negatives. Thought to be the least objective of the 3, since it is based on lab tech interpretation of the interaction between food sample and blood cells. Caveate: patient must have eaten the foods tested within the previous few months to get any sort of accurate result, otherwise results may have false negatives.

The gold standard for food allergy is the double-blind, placebo controlled, oral food challenge (done in the doctor's office). I'm not sure anyone has come up with a gold standard for intolerances, but a detailed food diary in which every ingredient of everything consummed, plus a notation of any symptoms that change or appear, may reveal patterns that can then be tested with elmination/re-challenge diets.

And of course they have to make it confusing and use "intolerance" to refer both to delayed reactivity to food and enzyme deficiency related problems (such as Lactose Intolerance, which is caused by a deficiency of the enzyme lactase needed to digest milk sugar).

There are some problems with the tests, too: food test serums are not standardized, therefore you may get different results depending on which lab runs the test, the immune system has natural variations from day to day that may influence how strongly you react on a test to a food, which could potentially mean the difference between being told you do not have an allergy or intolerance to a particular food, when running the test on a different day may have caused the food to show up on the test as positive. Also, some MD's interpret any reaction on a test (whether it is class 1 or class 4) to be a positive result, others may only consider class 1 to be insignificant, class 2 to be equivocal (borderline), and only consider class 3 and up to be allergies / intolerances. Best suggestion I can give is to make sure and ask for an actual copy of the test results, that way you can see for yourself what the tests show and can ask your doctor more specific questions about the results.

I hope this helps - take care,
-Razzle
Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD (Lupus?), Osteoporosis, Anemia,  Lymphopenia, chronic malabsorption/malnutrition, Lyme Disease (Igenex Lab IgM WesternBlot positive; & as of 7/25/08, IgM is CDC Positive!), etc.; Currently TPN-dependent.
Meds:  Zofran, Vitamin B12 Shots, Heparin (to flush PICC line).


damo123
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Date Joined Jul 2007
Total Posts : 709
   Posted 8/4/2008 2:13 PM (GMT -7)   
I did get a copy of the results and it showed my diary intolerance at 4 and my wheat intolerance at 3. I was told that a 4 was a very serious intolerance level and probably meant I could never handle dairy in my life again.

I told my doctor about this but he still seemed highly sceptical insisting that all of us have intolerances to certain foods which may or may not produce symptoms and he felt it not a good idea to run the risk of excluding something as important as dairy i.e. for calcium etc

Just confused as to how a medical doctor and an allergist can have polar opposite opinions on an issue that I thought would be highly objective.

Thanks for your advice.

D
Med free for a bit as I needed a break from Asacol
 
Probiotics
 
"Whatever you do in life don't berate yourself too much nor contragulate yourself too much. Your choices are half chance. So are everybody elses'"
 
 
 
 
 
 
 


Red_34
Forum Moderator


Date Joined Apr 2004
Total Posts : 23424
   Posted 8/4/2008 6:17 PM (GMT -7)   
D, I've had that happen on many occasions. My family doc will contradict what my specialist says but you know what? That is the reason we see a specialist in the first place - because they specialize whatever it is that you are seeing them for. The family doc has general knowledge but the specialist has special training in their field.
 @--->--SHERRY--<---@
Moderator for Allergies/Asthma and Co-moderator for UC
~Left sided Uc-'92-Colazal(9 daily),6mp(50-100mgs),Prilosec,Biotin,Forvia,Pro-Bio**Unable to tolerate Asacol, Rowasa or Canasa**~Year-round allergies-Singulair, Allegra~Secondary Reynauds Syndrome-'04-Norvasc~Spinal Stenosis(?)~Sacroiliitis-epidural injections~bulging and herniated discs C5/C6 & C6/C7~2nd epidural injection 8/14, Neurontin and Skelaxin
To help Healingwell - click here: DONATE
 
 
 
 

 
 


Razzle
Veteran Member


Date Joined Aug 2007
Total Posts : 4392
   Posted 8/9/2008 2:18 PM (GMT -7)   
The myth still exists that allergies are "all in the imagination" even though science has proven allergies are a real, physiological phenomenon. I'd trust the advice of the Allergist over the advice of the GP in this situation...a class 4 allergy is very strong indication that your body does not like that food.

Also, there are other ways to get Calcium:

Dark leafy green vegetables, broccoli, nuts & seeds, etc., are all good sources of calcium.

Vitamin D can also be obtained from other sources:

Certain fish/seafood, Sunshine (well, during Summer, anyway), and other fortified foods.

And there is always the option of taking Calcium & Vitamin D supplements.

Take care,
-Razzle
Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD (Lupus?), Osteoporosis, Anemia,  Lymphopenia, chronic malabsorption/malnutrition, Lyme Disease (Igenex Lab IgM WesternBlot positive; & as of 7/25/08, IgM is CDC Positive!), etc.; Currently TPN-dependent.
Meds:  Zofran, Vitamin B12 Shots, Heparin (to flush PICC line).


men8ifr
Regular Member


Date Joined Jul 2008
Total Posts : 124
   Posted 8/27/2008 3:46 AM (GMT -7)   
Any idea which type of test this is http://www.yorktest.com/en/buy-a-test/product-information/FoodScan113FoodIntoleranceTest.html?Productid=2

would people recommend doing it? I will have to start eating carbs again I guess since I have cut them out for quite a while - how long would i need to eat them for ?
Ian

6 Asacol tabs/day
1 Pentasa Suppository / day
Fish oil 3/day (omega 3 only)
Multivitamin and mineral 1/day
Folic Acid 1/day
Aloe Vera 3/day
Specific Carbohydrate Diet SCD
Turmeric 3/day
Currently in no mans land between flare and remission


SnowyLynne
Veteran Member


Date Joined Apr 2004
Total Posts : 1539
   Posted 8/27/2008 4:38 AM (GMT -7)   
I wouldn't worry what your primary thinks,listen to the allergist after all he'knows more about it,besides what if you listened to you pdoc & something bad happened if you ate something you shouldn't?Food for thought!!
SnowyLynne


Razzle
Veteran Member


Date Joined Aug 2007
Total Posts : 4392
   Posted 8/27/2008 12:36 PM (GMT -7)   
The York FoodScan113 is a test that looks for IgG subclass 4 antibodies to foods. http://www.yorktest.com/en/about-us/research/ gives a list of research studies showing potential benefits from following a diet that eliminates the foods that show positive on the FoodScan113. The choice is ultimately yours whether or not you have the test done. I would thoroughly read the website before making your final decision, so that you are fully aware of what the cost is (i.e, in the event your insurance doesn't cover the cost of the test) and the information available about the lab itself as well as what the test will and won't tell you. Call the lab and ask them what the time frame for eating the foods should be prior to taking the test - they are more equipped to answer that question than I am. Based on studies done for Celiac Disease, the time needed for the body to respond to the food again after a period of elimination likely will be different for each individual person.

Good luck,
-Razzle
Chronic Lyme Disease, Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD ("Secondary Lupus-Like Syndrome"), Osteoporosis, Anemia, Lymphopenia, intermittant Pancytopenia, chronic malabsorption/malnutrition, etc.; Currently TPN-dependent.
Meds:  Zofran, Vitamin B12 Shots, Heparin (to flush PICC line).

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