Thanks to all of you who responded to my query about placebo unmasking
at trial closure.
First of all, it looks like there is no standard procedure about
informing patients in the placebo arm that they had been allocated to a
placebo once the trial comes to an end.
Secondly, there appear to be only a handful of trials which have
followed up such patients who were informed of study arm.
These are included below, for anyone who is interested.
1. Follow-up study of patients randomly allocated ramipril or placebo
for heart failure after acute myocardial infarction: AIRE Extension
(AIREX)Study. Acute Infarction Ramipril Efficacy [see comments]. Lancet
1997; 349: 1493-7
2. Six-year follow-up of the Norwegian Multicenter Study on Timolol
after Acute Myocardial Infarction.New England Journal of Medicine.
313(17):1055-8, 1985 Oct 24.
Herlitz et al. The influence of early intervention in acute myocardial
infarction on long-term mortality and morbidity as assessed in the
Göteborg metoprolol trial. International Journal of Cardiology, 1986;
291-301.
***
LETTER SENT TO EVIDENCE-BASED-HEALTH
The double-blind placebo-controlled RCT is often considered to be the
gold standard technique used in order to evaluate the effects of
treatment, especially for drug trials.
There are two questions I would like to present to you regarding this
approach.
Firstly, I would like to find out whether there is a standard procedure
about informing the participants of double-blind placebo-controlled RCTs
what treatment arm was allocated to them, once the study is over.
Personally, I would say that patients should be given a choice during
the informed consent procedure about whether they would like to know.
But what happens usually ?
My second question attempts to 'tap' into the mechanisms of the placebo
effect. I would appreciate any information regarding studies which have
followed up patients of double-blind placebo-controlled RCTs - once the
treatment allocation was revealed to them. If the placebo effect is
'real', then placebo responders who are told they have been taking
'dummy' pills, should have some interesting psychophysiological reponses
!
Zelda Di Blasi
Research Fellow
Department of Health Sciences and Clinical Evaluation and
NHS Centre for Reviews & Dissemination
University of York
YORK YO10 5DD
Tel. 01904-434519/ 434575
Fax. 01904-434517/ 434556
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