Replies to post #110885 on Biotech Values

[biomaven0]

One of the most difficult and problematic sources of measurement error is the substantial placebo effect in pain trials. Upwards of 60% in some studies and routinely accounting for 30% of variance.

I've always thought that these sort of trials should use an initial wash-out period to weed out the placebo responders. You need to avoid participants knowing for sure they are on a placebo, so maybe a design like this:

Washout period has 3 arms:

10% placebo arm 1
10% drug arm 2
80% placebo arm 3

After the washout period you discard patients from placebo arm 3 that had a response, and you re-randomize the remaining patients from arm 3 to placebo arm 1 or drug arm 2.

Peter