Unblinding of trial participants to their treatment allocation: lessons from the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER).
BACKGROUND
The gold standard clinical trial design is the double-blind, randomized, controlled trial. No standard practice exists for the "unblinding" of trial participants and no legal obligation is placed on investigators to inform participants of their treatment allocation or study results at the end of a trial. Here we document our experiences of unblinding the 2520 Scottish participants in the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER).


METHODS
The objectives of the PROSPER unblinding process were to provide all study participants with their study medication status and on-trial cholesterol levels and to respect the rights of participants not to be unblinded. It was considered imperative by the study executive that the blind was maintained until the presentation and publication of the results. Staff therefore remained "blinded" throughout the unblinding process. Inappropriate contact with the PROSPER participants was avoided by confirming their current vital status and health status.


RESULTS
To coincide with the presentation of the PROSPER results, all participants, for whom it was deemed appropriate, were sent a summary of the results and were offered the opportunity to be advised of their treatment allocation and on-trial lipid profiles. The majority of participants opted for telephone unblinding. All primary care physicians who had patients randomised to the study were also sent a summary of the study results and sealed documents detailing the treatment allocation and lipid profiles for each patient. Relocated patients were traced and the information forwarded to their new primary care physicians.


CONCLUSIONS
The dissemination of study results and treatment allocation to study participants is an integral part of the research process and should be included in the design of any clinical trial.
Dinnett
Eleanor M
EM
Clinical Trials Unit, Glasgow Royal Infirmary, Glasgow, UK.
Mungall
Moira M B
MM
Kent
Jane A
JA
Ronald
Elizabeth S
ES
McIntyre
Karen E
KE
Anderson
Elizabeth
E
Gaw
Allan
A
D000368:Aged; D000924:Anticholesteremic Agents / Q000627:therapeutic use*; D001294:Attitude to Health; D002784:Cholesterol / Q000097:blood; D030881:Disclosure; D004311:Double-Blind Method; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use*; D028701:Patient Rights; D018579:Patient Selection; D010821:Physicians, Family; D010919:Placebos; D017035:Pravastatin / Q000627:therapeutic use*; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D012307:Risk Factors; D014652:Vascular Diseases / Q000517:prevention & control
D000924:Anticholesteremic Agents; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D010919:Placebos; D002784:Cholesterol; D017035:Pravastatin