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Author Topic: "Gold Standard" DBPCFC  (Read 2784 times)

Description: Double-Blind Placebo-Control Food Challenge

aouda

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"Gold Standard" DBPCFC
« on: October 28, 2011, 04:38:56 PM »
[Hello all,  :bye: first post here] I've read many papers where the DBPCFC is called the gold standard test to see if someone should not be diagnosed as allergic to something anymore.  But I am wondering who exactly is blind in a peanut challenge.

How do you hide something like several grams of peanut flour in a small amount of food (that can be eaten in ~10 min) so that that the presence/smell of peanut and oat flour really remains blind to both researcher and subject?  I think I could easily smell even 0.5g of peanut flour mixed in applesauce or yogurt a mile away.   I guess they would have to mix each into about a 0.25 - 0.5 cups of Sunbutter in order to obscure peanut to me.  Do they make everyone wear clothespins on their noses?

Like in the following paper [J ALLERGY CLIN IMMUNOL, VOLUME 127, NUMBER 3, VARSHNEY ET AL. (bolding mine)], the maximum single dose is 4000mg if the child makes it that far.   Is it reasonable to assume that no one can tell at any point within the challenge?  (Sorry if this has been discussed before elsewhere -- if anyone sends me a link, I will be happy to follow it.)

Build-up visits. Subjects returned every 2 weeks for approximately
44 weeks for dose escalations. Doses were increased by 50% to 100% until the
75-mg dose and were then increased by 25% to 33% until the 4000-mg
maintenance dose was reached
.

Maintenance phase. After reaching the maintenance dose of
peanut flour or placebo, subjects ingested the dose daily for 1 month and
then returned for the first oral food challenge (OFC) at week 48.

OFC
A double-blind, placebo-controlled food challenge was performed after 4
weeks of maintenance therapy. Before the OFC, subjects were asked to restrict
the use of antihistamines, b-agonists, theophylline, and montelukast.16 All subjects
were challenged to both peanut and oat flour in a blind manner. Challenges
were administered by a nurse or physician who was also blind to the testing materials.
The challenge consisted of peanut or oat flour given in increasing doses
every 10 to 20 minutes up to a cumulative dose of 5000 mg protein.

aouda

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Re: "Gold Standard" DBPCFC
« Reply #1 on: October 31, 2011, 08:32:47 AM »
Anyone who was ever present at a peanut challlenge have any thoughts?

Offline CMdeux

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  • Member
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  • Posts: 31,861
  • -- but sometimes the voices have good ideas!
Re: "Gold Standard" DBPCFC
« Reply #2 on: October 31, 2011, 11:41:08 AM »
Okay-- we've never done a PEANUT challenge.

But I can tell you that we HAVE done a single-blinded food challenge.  My daughter did NOT know when the switchover from control to experimental sample occurred.

The patient generally cannot tell which is the negative control initially, which is where you'd expect to see any psychosomatic symptoms manifest.  Ergo, that really is the point in most food challenges.



I realize that no, this doesn't really address "blind" dosing in a TRIAL.

You could check with Mommabridget-- her son is involved in a peanut desensitization trial, and they had initially been in the sham treatment (placebo, or control) group, and they were pretty confident that this was so by about a month into things.
  The "why" of that I'll leave to her.

But yes, it is generally not completely unclear to the patient once the doses become larger than maybe 500 mg (much lower, of course, for someone who remains fully allergic), even if it is unclear to the physician/researcher.
 

Resistance isn't futile.  It's voltage divided by current. 

Western U.S.