Also influencing whether you decide to mask is the
type of outcome you have chosen for you trial.
What are the primary outcomes?
If they're very objective outcomes it's probably less important to mask.
Certainly the most objective outcome is whether a participant alive or dead.
And then, in that situation it's not as likely to be influenced
by people's opinions about the treatment.
So the more the subjective the outcome, the more
you should be thinking about trying to mask the treatment.
So if you're asking for patients evaluation of how they
feel, certainly in pain studies, it's very important to mask.
But sometimes, even when the outcome can be fairly subjective
you may not need to mask, or you can maybe institute
some bias control without masking the participants
by masking the people that evaluate the outcome.
So the people that are looking at the X-rays
or the MRIs don't know the, the treatment assignment.
So they won't be influenced.
I've done a lot of ophthalmology studies where we're taken different images of the
eye, the retina, and we haven't been able to mask a number of those studies
because of the invasiveness and the different modes of treatments.
You know, in some cases we had surgery where we put medicine in peoples eyes.
But even though we weren't able to mask the treatment
at the level the participant or the clinical investigator applying the
treatment, we were able to mask the reading center that
looked at the images and evaluated how the treatment was doing.
So it's also another thing to think about
is, what's the comparison group?
Is it a no treatment observation, or an active control?
If you're giving someone an active treatment, you
create some expectation about that this will help them.
So, it may be less important if you're comparing two active treatments
to mask than if you're comparing an active treatment to no treatment.
Because, in the no treatment
group, people know they're not getting treatment and there's some meaning
to just getting treatment that may help people have better outcomes.
Certainly you have to think about whether it's feasible.
What's the cost of masking?
What's the benefit?
Are you going to be able to do it effectively
enough to be worth the cost and is it practical?
Sometimes you're requiring participants to take
multiple doses of medication, in these kind
of double dummy designs.
And so, are participants going to adhere to it?
You know, it's hard enough to get people to take
a pill each day, much less have them take four.
And you really have to think about the practicality of it.
So, as I said in considering the ethics of masking, you
have to have a unmasking plan, if you do mask a trial.
And there's two types of unmasking
that comes up. There's the unmasking that's planned.
When the participant has completed the trial you certainly
want to let them know what treatment they were on.
Especially if they may want to continue with that
treatment if they felt that they were doing well.
And so this slide goes over that kind of unmasking.
And the strategy depends on the close out design.
So you can have a common close out design when you may enroll
patients over a period of time, but you're going to follow
everybody to a common closeout within, let's say, a month.
So, people may have different amounts of follow up time, depending on when they
were enrolled in the trial, but the
trial's going to end in November of 2010 regardless.
So, at that, you can sort of plan to
shut down all operations in terms of actively following people.
And you can have a close-out
visit and sort of inform everyone, around the same time.
But more commonly we have anniversary close out.
Where participants enroll in a trial and are followed for
a specific length of lime, let's say for six months.
So, you may be enrolling for a trial over a few
years, but than each participant is only followed for six months.
So you have people finishing the trial as you're continued to enroll.
So that's a little more difficult.
Because you don't want to be revealing the treatment assignment
to the clinic staff in a double mask trial.
But you do have an obligation to reveal it to the participant.
So things we've used is letters to participants at the exit interview
that we also have a letter that goes to their study physician in.
Of the asthma trials I've been involved in, and with
instructions on how to continue the treatment if they were
pleased with it.
Also in terms of unmasking, you should plan to find out information on what the
participant and the clinical personnel thought the
treatment assignment was before you can reveal it.
It can be informative about how effective your masking regimen was.
And it's important that you document the procedure.
And that you provide the participant and
their primary care providers with as much informsh,
em, mation, as you can about their status at the end of the trial.
It may be things like giving them the
results of tests that were done during the trial.