RAST, SPT & OFC What does it all mean? How do I prepare?

by Amanda Painter, South Chapter Coordinator

Allergy testing is part of managing food allergies.  Test results can help with diagnosis and also help monitor allergies over extended amounts of time for the possibility of outgrowing an allergy. 

Which type of test used depends on the uniqueness of the patient and what the allergist feels is best for the situation.   Knowing what to expect for each of these tests will help relieve some anxiety leading up to the day of testing.

RAST  
This is a blood test that measures IgE antibodies to particular foods.  Blood will be drawn at your allergist’s office or at a lab.  Test results will be sent to your doctor several days later.  Antihistamines do not affect blood tests.  This is helpful for those that find it difficult to stop their daily dose of maintenance allergy medicine. 

SPT
Skin Prick Test is what it sounds like.  The allergist will place a drop of solution containing the suspected food on your forearm or back.  Then there will be a gentle prick or scratch allowing the solution to go just under the surface of the skin.   Be sure to check with your allergist about what medications (especially antihistamines) you should discontinue (and for how many days) before this test.

Neither RAST nor SPT have a guarantee of being 100% accurate.  It’s important that the results are interpreted by a board certified allergist and that the patient history is also taken into account before removing foods from you/your child’s diet. 

OFC
Oral Food Challenge.  This is considered the “Gold Standard” for diagnosis.  OFC will take place in a medical setting, like an allergy office or hospital.  The patient will receive carefully measured doses of suspected food allergen, starting small and gradually increasing the dosage.  The patient is closely monitored for any signs of reaction.  Blood pressure, heart rate and respirations will be monitored during the challenge.  This test can take up to 3-4 hours.

Read more about allergy testing here:
http://www.joinfacet.com/diagnosis-and-testing.html

Now that you know the difference in the testing, I’ll share some tips for preparing for each of them. 

RAST- There isn’t much to do for this in terms of preparation.  Some people handle having blood drawn well and others don’t.  When it comes to dealing with children, I find that when it’s age appropriate, talk to them about what’s going to happen beforehand.  (Right beforehand, not 3 days before – that allows too much time for worrying and anxiety to increase).  I also feel that these are times that bribes or special treats may be warranted.

SPT- This test isn’t painful, but it can be uncomfortable if the arm or back is incredibly itchy.  For children, bring entertainment.  Something for them to hold in their hands will help reduce the temptation to scratch with their hands.  It will also help distract them from itching.  For infants and toddler, it’s good to dress them in 2 piece clothing allowing just the shirt to be removed for the testing.  Being able to keep pants on will help if the office is cool.

OFC - This is (in my opinion) the most difficult of all the tests to prepare for; mentally and emotionally.  Scheduling an appoint to have your child (or yourself) eat something that has been strictly avoided due to the possibility of a life-threatening reaction goes against everything you’ve been doing in your day-to-day food allergy management. 

As a parent this is an exciting time and full of hopeful possibilities, but also one filled with dread.  And those are just your emotions!  Then you realize you have a child that you have to prepare for this.  THAT is the challenging part. 

Depending on the age and emotional history of your child, you may question whether or not to tell them what is happening during the food challenge.  This is a decision that has to be made carefully.  I knew my daughter wouldn’t believe or accept any of my excuses for what we were doing in the allergist office besides the truth.  But I also have a friend whose son verbally protested, “they’re trying to kill me” as he attempted to run away during an OFC.  You may also question telling your child due to their emotional state.  If their anxiety normally runs high and fully informing them about the food challenge could cause a panic attack, where some symptoms mimic an anaphylactic reaction (think difficulty breathing and sense of impending doom). 

What to bring- Lots! 
Entertainment - You’re going to be there for a while.  Bring plenty to entertain your child (and yourself).  Electronics, coloring, crafts, books, card game, and small puzzles are all good items.

Clothes – bring an extra layer for you/your child and maybe a small blanket. Doctor’s offices can be chilly at times.  Also, bring an extra set of clothes for both you and your child.  We hope it doesn’t happen, but vomiting could be likely if your child reacts during the challenge.  Clean clothes will help both of you feel better. 

Be prepared to move around – it is recommended that the patient get up and move every so often during the challenge (this is to make sure everything is circulating well in their system.)  To keep my child entertained doing this we more than walked a lap around the office.  We bunny hopped, took big steps and little steps, high kicks, and did jumping jacks.

Support – let friends and family know what you’re doing.   My two best “food allergy friends” kept in touch with me through our entire challenge, in addition to my amazing extended family.  I received supportive texts, questions of how far we were in the process, how my daughter was handling it, how my anxiety was through multiple hours at the office.  Believe me, it helped!

Try to not let your anxiety get the best of you, and don’t let your child know how anxious you are.  Remember that you are in a structured and controlled environment, filled with medical professionals that are there to help you.  If a severe reaction occurs, you are with people that are prepared to help you and your child. 

Preparation is such a large part of managing food allergies.  Preparing for testing is no different.  Hopefully, these tips will assist you in feeling more prepared before heading to the allergist's office for testing. 

What other tips do you find helpful for allergy testing?