Wednesday, December 15, 2010

Testing

At out latest appointment we decided to redo some of our blood tests to check Bee's IgE levels.

We decided to have another RAST blood test done.  This is a simple blood draw.  The blood is tested for elevated IgE levels in reactions to certain foods.  This is safer than a skin prick test or a food challenge for people who are highly allergic like Bee.  Unfortunately, the test is not always 100% accurate, especially in children.  There can be false negatives, and a positive result or an elevated IgE level does not necessarily indicate a true allergy.  The skin prick test can also have false positives.  The most accurate test is a food challenge....scary!

Because there are fewer studies done with children in regards to food allergies, some of the blood tests for certain foods is less accurate.  However, according to our doctor, the tests for wheat, egg white, dairy, and peanut are the most accurate of the foods tested through blood work.  We decided to have those foods tested along with several other foods to compare her levels to our previous tests.

In our first RAST test, Bee's level of IgE for those 4 foods was extremely elevated, with wheat having the highest results.  We're now wondering if her results for wheat will have dropped and if her dairy results will still be high as she seems to have the most problems with dairy.  However, with IgE blood tests, the level of IgE to a certain food does not necessarily indicate how severe a reaction will be.  Even with a positive result, a person may not even show a reaction to a certain food.  For example, in our last RAST test, Bee had a positive result to several types of legumes.  She now eats all types of legumes without any problem, yet her test was still positive.  People can have a positive result against any food, with or without a reaction, and can even have a positive result after outgrowing an allergy.

We had a false negative result in our original RAST test as well.  Bee did not have elevated IgE levels to tree nuts.  I began avoiding peanuts and allowed our other children to have other nut butters as a safer alternative.  I did not allow Bee to have any type of nuts just in case.  One day she accidentally touched some of Tiger's almond butter and got some on her face.  She had a severe allergic reaction and we ended up at our local fire station with Bee on some oxygen.  Bee is definitely allergic to tree nuts even though her results were completely negative.  In June we had a skin prick test to test for an almond allergy and her results were very positive, confirming the allergy.  However, in our skin prick test, Bee had slightly positive results for oranges, which she has eaten without any problems.  The skin prick tests can be less accurate in people who have eczema, like Bee, because the skin problems make the test results more difficult to read. 

Allergy testing is confusing, sometimes inaccurate, and can be very frustrating.  We've learned to keep a record of what Bee has eaten and to watch for reactions after coming into contact with new foods-whether on purpose or on accident.  Our experience has to be our best guide.

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