Confusing RAST and SPT test results....


So... With the whole great big daycare debacle and their choice not to be peanut free, i figured that the first bite of eating my elephant should be having DS allergies actually diagnosed, by an allergist, so that i would have at least that to stand on.

I received the RAST results 2 days ago - he tested negative for everything on the VERY extensive panel, INCLUDING peanuts (however, on this extensive panel, nowhere did it contain orders to test for treenuts - can't fix stupid, right?). As much as I told myself not to get excited because there ARE false negatives, and even though I knew in my heart that he IS allergic, somehow I allowed myself to hope hope HOPE that I was wrong and that his FAs were simply a figment of my imagination. Let me tell you, I would have stood on my rooftop telling the world how wrong I was if that was the case. So, even though i really didnt want to subject ds to a SPT, i felt it really was necessary at this point, so that we can know, one way or the other.

the allergist did a lousy job explaining the results, and each time that i said i didnt understand why the results were what they were, he explained it the SAME exact way (which obviously i wasnt comprehending....)... so the med asst performed the test, and i sat there absolutly sobbing as my 11m ds cried and just looked at me like mommy, this hurts so bad! and i sobbed even harder as i watched his arm grow red, and the welts raise up. i wish they hadnt told me the rast was negative, because it crushed me to watch welt after welt raise up.

The results were this: (from the chart he wrote it on, each allergen has a box, and a space for "I" and "E" -does anyone know what this means? - maybe the size of the wheal?)

Negative Control - 0 Hazelnut - 0 Cows Milk - 0 Oat - "E" 5x5 Peanut - 0 Coconut - "I" 2x2 "E" 4x4 Pecan - "E" 5x5 Walnut - "I" 2x2 "E" 5x5

Yet, the doctor still told me that my son is in fact allergic to peanuts and tree nuts (which he hasnt ever had a reaction to before, and i've never been cautious about washing my hands after touching/eating nuts before, as he HASNT ever had a reaction).. The dr seemed to be saying that he just didnt have the antibodies in him, but he still is allergic and that makes no sense to me? Can someone with testing experience under their belt explain why rast and spt came out negative for peanut but he is still allergic and has had reactions, AND why he is showing spt allergic to treenuts with no history of reactions? If those are the measurements of the wheal, is that considered a sizeable reaction, normal, or low? would it be worth subjecting him to a blood draw again in order to get his rast # to keep track of?

On Feb 29, 2008

another quick question - at this point, would you guys avoid seeds (ie sunflower) and seed oils (sunflower oil)?

On Mar 3, 2008

does anyone have any info theyd be willing to share on this? i am still SO confused, and even had a follow up phone call w/ allergist with no more explanation (at least in a way that made sense!)... and growing more confused by the day!

On Mar 4, 2008

When I was getting tested for PNA and TNA, my allergist told me to not take any antihistamines 7 days before the test. I followed that for the SPT (which I had first) and but didn't follow that for the RAST (I had a reaction 3-4 days before my RAST was done. My RAST came back negative on everything, even though, I knew I was allergic, I had multiple reactions to both before. If your child had any antihistamines (there were other medications too) with in a week before the RAST was done, that may be why the results were negative. Hope this helps

On Mar 4, 2008

it was my understanding that the RAST should not be affected by antihistamines, that it only affects SPT, and I was told only 24 hours no antihistamines prior to SPT. In any event, he doesn't take any medication regularly, and though there is a very slight chance he could have had a dose of benadryl in the week timeframe (its been awhile, my memory isnt THAT good!), it DEFINATLEY wasn't within 24 or even 48 hours...

i am just SO confused and DONT GET IT! rast was completely negative on peanut, not tested for treenut, SPT showed reaction to TN but not PN! what is the deal?!?!

~confused mama!

On Mar 4, 2008

He could be severly allergic to tree nuts and not allergic to peanuts. They are completely different families of foods. If he reacted to peanuts/peanut butter it could be that it was something that was cross-contaminated with tree nuts, and that triggered the reaction.

If the RAST and the SPT for Peanuts were both negative, then you could always consider a food challenge if you really need confirmation.

You also may want to consider seeing another allergist, if this one can't explain things to you. You want to be comfortable with your doctor.

On Mar 4, 2008

okay, a little background (sorry for those of you whove heard it before!), i developed PA but not TNA while pregnant (went away after i delivered). DS's first reaction was to nutella, which is mostly peanut oil and hazelnut. i chalked it up to the peanut oil, probably correctly, as his SPT for hazelnut was negative (of the few nuts they tested, he tested positive for pecan, walnut and coconut). his second, more severe reaction was to a reeses PB cup that i had eaten, and then touched him. so yes, i suppose it could have been cross contam, but it seems unlikely to me. ALSO, up until he was tested we had eaten tree nuts in the house all the time (how irresponsible of me, but i honestly believed he was PA only!), including pecans, almonds and cashews... with ZERO reaction and were never careful about washing hands before touching him, etc.

he is way too little for an oral challenge (imo at least), he will be a year next month... so i guess at his 1 year well baby i will ask for a referral to another allergist.. its just the more i think about it, the crazier i feel, and the more confusing it gets! thank you for the replies so far though! everyone on here is so incredible!