When planning a randomized, double-blind trial with multiple arms, there are often challenges for blinding the study treatment/groups due to different formulations/packaging/dosage.
E.g. Study groups
1. treatment A- (spray bottle)
2. treatment B- (drops)
3. treatment C- (drops)
4. Active comparator- (drops)
5. Placebo- (both options possible- spray bottle/drops)
Instead of a double-dummy approach, can we follow group blinding with two or more blinding practices in the same trial?
One blinding group is for treatment A and Placebo as spray bottles.
The blinding second group is for Treatment B and C and Active as drops.
The objective of blinding is to keep the subject and investigator/study team unaware of the treatment assigned, and the same can still be met with the above (with certain limitations of course...)
If you know of any reference trial with such an approach, kindly share.
Thanking you in anticipation.
Devang P Parikh
Dear Dr. Parikh,
Many thanks for your challenging question. After reading and consulting, I want to tell you some points that hope will be as helpful as possible.
Yes, you can have two or more blinding methods; however, please pay attention to the aims you are looking for. It seems that in this double-blind trial, two situations can occur as follows.
1) In the first situation, a group of patients is told that if they agree, they will randomly receive one of the treatments under study (T.A, T.B, or T.C), an active comparator, or a placebo in the form of a spray. An observer is assigned to this group, who observes and records the outcomes after the patients receive the spray, while does not know whether the spray is T.A or placebo. Therefore, neither the patients nor the observer know about the contents of the spray, so double-blind occurs.
2) In the second situation, another group of patients is told that if they agree, they will randomly receive one of the treatments under study (T.A, T.B, or T.C), an active comparator, or a placebo in the form of a drop. Another observer is assigned to this group, who observes and records the outcomes after the patients receive the drop, while does not know whether the drop is T.B, T.C, active comparator, or placebo. Therefore again, neither the patients nor the observer know about the contents of the spray, so double-blind occurs.
However, please note that the only unblinding can occur is that the observer of the group receiving the drops realizes that, for example, the form of spray generally works better than the form of drop, and thus records and reports the unpleasant outcomes of the drops slightly higher. In this sense, information bias may occur. However, observers in each situation cannot differentiate between treatment, placebo, and/or active comparator.
It would be my pleasure if I have comments on this discussion.
Best regards,
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