[ASusan]

OK MDC mamas - a research challenge. I've been googling for over an hour and I can't find the false negative rate for skin prick tests. I can find *reasons* for false negatives (e.g., child took an antihistamine, allergic solution too weak, poorly administered test), but not an estimate of how often false negatives occur.

Any information, with links, would be appreciated. Thank you.

 

[Chinese Pistache]

I have no idea the rates, I've just been told by an allergist and read in numerous places that it happens less often the older the child is. So, after age 4 or 5, you're more likely to get a true result.

 

[WuWei]

I believe the incident of false negative skin prick test, may vary according to allergen. For instance, dairy may have a false negative incident of x%. But, wheat may have a false negative incident of y%.

Even within "dairy", there are different types of casein, A1 and A2, for instance. So, if you skin prick test one of those, it may not apply to the other type of casein.

Same with wheat, sprouted wheat, GMO-wheat, etc. Also, the conduit substrate which preserves and imparts the allergen could deteriorate over time, based on many variables...

This report describes some of the various testing issues. http://findarticles.com/p/articles/m..._/ai_n14899860

This informative articles reports, "A negative prick skin or RAST test predicts with about 97% accuracy that the test food was not the cause of symptoms but only in atopic disorders and where immediate hypersensitivity food reactions are involved."
http://www.allergyclinic.co.nz/guides/11.html

(which doesn't answer your question, lol)

Here is another report, specific to "milk", for example. "In the literature, the positive predictive accuracies of skin prick tests vary between 69 and 100% and the negative predictive accuracies between 20 to 86% for cow's milk."
http://www.ncbi.nlm.nih.gov/pubmed/1...?dopt=Abstract

Ah-ha, found this!

Skin Prick testing: Good for telling what you are NOT allergic to but not what you ARE allergic to (low positive predictive accuracy, good negative predictive accuracy). (Skin prick testing is not paid for by Medicare.
http://www.entusa.com/_themes/intrum...m/indbul3a.gif
For milk and eggs, the testing results are approximately 50% false positive but less than 5% false negatives. For peanuts, 70% false positive and 10% false negative rate. No correlation between skin test size and severity of reaction. (Sporik R, et al. Clinical Exp Allergy 2000; 0:1540-6) View Abstract

http://www.entusa.com/_themes/intrum...m/indbul3a.gif
Skin Prick testing to nuts � 46% of those tolerant to nuts had a positive skin prick test as only 0.5% of those clinically allergic to nuts had a negative test. (Clark at, Ewan PW. Clinical Exp Allergy 2003; 83 1041-45) View Abstract

This site seems to reference actual studies related to accuracy of different allergy testing alternatives. http://www.entusa.com/food_allergy.htm

Pat

 

[isaoma]

WuWei has a much more informed answer than mine.

But, I have also read somewhere that the false positive for wheat was pretty high too. Also, if your child has any sort of skin reaction already i.e. eczema, that can cause a high false positive rate because the skin is already sensitized and reacting to some allergen.