Participants in randomized trials sometimes prefer to be assigned to one arm rather than another. While randomization aims to ensure that participants with different preferences are spread equally among the arms of the trials, it cannot always address the possible effects of participant preferences on outcomes, compliance, and attrition. This paper discusses the conceptual, design, and statistical complications associated with preference effects and evaluates a number of experimental designs that have been proposed to gauge and minimize the effect of participant preferences.
Adamson, Joy, Sarah Cockayne, Suezann Puffer, and David J. Torgerson .2006. Review of randomised trials using the post-randomised consent (Zelen’s) design. Contemporary Clinical Trials27:305-19.
2.
Brewin, Chris R., and Clare Bradley.1989. Patient preferences and randomised clinical trials. BMJ299:313-15.
3.
Cooper, Kevin G., Adrian M. Grant, and Andrew M. Garrett .1997. The impact of using a partially randomised patient preference design when evaluating managements for heavy menstrual bleeding. British Journal of Obstetrics and Gynaecology104:1367-73.
4.
Hewitt, Catherine, David J. Torgerson, and Jeremy N. V. Miles.2006. Is there another way to take account of noncompliance in randomised controlled trials?Canadian Medical Association Journal175 (4): 347-84.
5.
John, Peter, and Tessa Brannan.2008. How different are telephoning and canvassing? Results from a "get out the vote" field experiment in the British 2005 General Election. British Journal of Political Science38 (3): 565-74.
6.
King, Michael, Irwin Nazareth, Fiona Lampe, Peter Bower, Martin Chandler, Maria Morou, Bonnie Sibald, and Rosalind Lai .2005. Conceptual framework and systematic review of the effects of participants’ and professionals’ preferences in randomised controlled trials. Health Technology Assessment9 (35): i-xi, 1-186.
7.
Luellen, Jason K., William R. Shadish, and M.H. Clark.2005. Propensity scores: An introduction and experimental test. Evaluation Review29:530-58.
8.
McPherson, Klim, Annie R. Britton, and John E. Wennberg .1997. Are randomised trials controlled? Patient preferences and unblind trials. Journal of the Royal Society of Medicine90:652-56.
9.
O’Rourke, P. Pearl, Robert K. Crone, Joseph P. Vacanti, James H. Ware, Craig W. Lillehei, Richard B. Parad, and Michael F. Epstein .1989. Extracorporeal membrane oxygenation and conventional medical therapy in neonates with persistent pulmonary hypertension of the newborn: A prospective randomised study. Paediatrics84:957-63.
10.
Paluck, Elizabeth L.2009. Reducing intergroup prejudice and conflict using the media: A field experiment in Rwanda. Journal of Personality and Social Psychology96 (3): 574-87.
11.
Preference Collaborative Review Group.2008 . Patients’ preferences within randomised trials: Systematic review and patient level meta-analysis. BMJ337; a1864.
12.
Shadish, William R., Thomas D. Cook, and Donald T. Campbell .2002. Experimental and quasi-experimental designs for generalized causal inference. Boston: Houghton Mifflin.
13.
Torgerson, David J., Jennifer A. Klaber-Moffet, and Ian T. Russell .1996. Patient preferences in randomised trials: Threat or opportunity. Journal of Health Services Research and Policy1:194-97.
14.
Torgerson, David J., and Martin Roland.1998. Understanding controlled trials: What is Zelen’s design?BMJ316 (7131): 606.
15.
Torgerson, David J., and Bonnie Sibbald.1998. Understanding controlled trials: What is a patient preference trial?BMJ316 (7128): 360.
16.
Torgerson, David J., and Carole J. Torgerson .2008. Designing randomised trials in health, education and the social sciences. Hampshire , UK: Palgrave Macmillan.
17.
Wennberg, John E., Mike J. Barry, Jack Fowler, and Al Mulley.1993. Outcomes research, PORTS, and health care reform. Annals of the New York Academy of Sciences703:52-62.
18.
Zelen, Marvin.1979. A new design for randomised clinical trials. New England Journal of Medicine300: 1242-45.
