A ? about oral challenges

Posted on: Fri, 03/05/2004 - 12:24am
Scared Nutless's picture
Joined: 01/13/2004 - 09:00

I've done a search but I haven't been able to find out what a "double blind oral challenge" is or a "double blind placebo controlled challenge" is. This is not something I would consider for dd...just curious. Can anyone explain for me what these terms mean? Or can you direct me to a website where these explanations are given? Thanks!

Posted on: Fri, 03/05/2004 - 12:34am
momma2boys's picture
Joined: 03/14/2003 - 09:00

What Is a Controlled Food Challenge?
In a controlled environment such as an intensive care hospital unit, the doctor (usually a board-certified allergist) may conduct a food challenge test to determine if a food allergy exists or to confirm a suspected food allergy.
A sample of the suspected offending food is given to the person unknowingly. The suspected offending food may be mixed with another food or may be disguised as an ingredient in another food. These food preparation techniques are used to prevent undue influence on the outcome of the test (if the person recognizes the food by sight or taste). Another method is to have the person take a capsule containing the allergen.
This test is given under strict supervision. After eating the food or taking the capsule, the person is monitored to see if a reaction occurs.
The ideal way to perform the food challenge test is as a "double-blind, placebo-controlled test." With this method, neither the allergist nor the allergy sufferer is aware of which capsule, or food, contains the suspected allergen. In order for the test to be effective, the person must also take capsules or eat food that does not contain the allergen. This will help the allergist make sure the reaction, if any, being observed is due to the allergen and not some other factor.
Someone with a history of severe reactions cannot participate in a food challenge test. In addition, multiple food allergies are difficult to evaluate with this test.
Since this test takes a lot of time to perform, it is costly and thus, done infrequently. This type of testing is generally used when the doctor needs to confirm or eliminate specific food allergens.
Hope this helps!
[This message has been edited by Chris (edited December 20, 2005).]

Posted on: Fri, 03/05/2004 - 1:38am
Scared Nutless's picture
Joined: 01/13/2004 - 09:00

Very much so! Thank you Momma2boys!

Posted on: Fri, 03/05/2004 - 2:48am
ajinnj's picture
Joined: 05/13/2003 - 09:00

What is a Food Challenge?
By Dan Atkins, M.D.
A food challenge consists of having a patient eat a food suspected of previously causing symptoms in a controlled fashion under medical supervision. The basic structure of a food challenge involves feeding gradually increasing doses of the suspected food at predetermined time intervals until symptoms occur or a normal portion of the food ingested openly is tolerated.
The history of previous suspected reactions to the food is reviewed and an interval history is taken to insure that the patient is stable. Performing a food challenge in a patient whose asthma is not well controlled is contraindicated. Obviously, a food challenge should be postponed if the child is thought to be coming down with another illness to avoid confusing results or the potential for an accelerated reaction. Vital signs, spirometry and a physical examination are performed before starting the challenge and prior to subsequent doses or whenever the patient complains of symptoms.
Food challenges come in a variety of flavors and are categorized into open, single-blind placebo-controlled or double-blind placebo-controlled depending upon who knows what the patient is receiving in each dose during the challenge.
In an open food challenge (OFC), both the patient and medical staff are aware that the patient is eating the suspected food. For example, a child receiving an OFC to egg might be given increasing doses of scrambled egg every 30 minutes until a whole egg is ingested.
In a single-blind placebo-controlled food challenge (SBPCFC) the medical staff is aware of what the patient is being fed, but the patient is not. A child receiving a SBPCFC to egg receives egg masked by concealing it in another food. The medical staff knows if and how much egg is contained in each challenge dose, but the patient and the patient's family do not. Each dose could either contain concealed egg or be a placebo. However, the final dose of any food challenge is the open ingestion of a normal portion of the suspected food. SBPCFCs are performed to eliminate bias on the part of the patient and/or the patient's family. In a double-blind placebo-controlled food challenge (DBPCFC) neither the patient nor the medical team involved in administering the challenge is aware of what the patient is being fed.
The DBPCFC is performed to eliminate both patient and observer bias. For the safety of the patient at least one physician not directly involved in the challenge must be aware of the challenge contents even in a DBPCFC. Again, the final dose of the DBPCFC is a normal portion of the suspected food ingested openly.
A food challenge is completed when the patient has an obvious reaction to the food or when a normal portion of the food has been ingested openly without symptoms. The length of time a patient is kept for observation after completion of the challenge depends upon several factors including the timing and severity of previous reactions and any concern about biphasic anaphylaxis. The results of the challenge should be thoroughly reviewed with the patient and his or her family and all questions should be addressed in light of the findings of the challenge.
This HealthTip was updated on March 1, 2002

Posted on: Fri, 03/05/2004 - 3:45am
ajinnj's picture
Joined: 05/13/2003 - 09:00

I've had a double blinded food challenge when entering the tanox peanut study. The challenge was done in two separate days, one day was "placebo day" and the other was "peanut day". Neither I nor the staff knew which day was which (until I reacted then it was quite evident). I was given capsules either containing placebo or peanut flour. The capsules were dipped in peppermint oil so I could not taste the peanut. The nurse told me one person actually reacted on the wrong day-- probably from nerves.

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