Is recruitment more difficult with a placebo arm in randomised controlled trials? A quasirandomised, interview based study

BMJ 1999;318:1114-1117 ( 24 April )

General Practice

Is recruitment more difficult with a placebo arm in randomised controlled trials? A quasirandomised, interview based study

A J Welton, health psychologist, ^a M R Vickers, senior scientist, ^a J A Cooper, statistician, ^a T W Meade, professor, ^a T M Marteau, professor. ^b

^a Medical Research Council Epidemiology and Medical Care Unit, Wolfson Institute of Preventive Medicine, St Bartholomew's and Royal London Hospital School of Medicine and Dentistry, London ECIM 6BQ, ^b Psychology and Genetics Research Group, King's College London, Guy's Campus, London SE1 9RT

Correspondence to: Ms A J Welton a.j.welton{at}mds.qmw.ac.uk

Objective: To investigate whether including a placeboarm in a clinical trial of hormone replacement therapy influencedwomen's stated willingness toparticipate.
Design: Quasirandomised, interview basedstudy.
Setting: 10 group practices in the Medical ResearchCouncil's General Practice ResearchFramework.
Participants: 436 postmenopausal women aged 45-64 who hadnot had ahysterectomy.
Main outcome measures: Stated willingness to enter a trial and reasonsfor the decisionsmade.
Results: Of 218 women told about the trial withouta placebo arm, 85 (39%) indicated their willingness to enter comparedwith 65 (30%) of the 218 women told about the trial with the placeboarm (P=0.06). Part of this difference was due to explicit reluctanceto take a placebo. Altruism and personal benefit were the reasonsmost frequently given for wanting to take part in a trial. Thereasons most frequently cited for not wanting to take part werereluctance to restart periods, not wanting to take unknown orunnecessary tablets, or not wanting to interfere with presentgoodhealth.
Conclusion: For preventive trials the inclusion of a placeboarm may reduce patients' willingness toparticipate.

Key messages

Recruitment to a clinical trial of hormone replacement therapy was lower when there was a placebo arm
The most common reasons for wanting to take part were to help medical research, to help women in the future, and personal benefit
Including potential benefits for other people in patient information, as well as personal benefits and risks, may increase recruitment

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