Is recruitment more difficult with a placebo arm in RCTs?BMJ 1999; 319 doi: https://doi.org/10.1136/bmj.319.7213.853b (Published 25 September 1999) Cite this as: BMJ 1999;319:853
Methodological issues will have affected results
- Lindsay Forbes, lecturer in public health medicine (firstname.lastname@example.org),
- Sue Chinn, reader in medical statistics,
- Jose Figueroa-Munoz, lecturer in public health medicine,
- Paul Seed, lecturer in medical statistics
- Department of Public Health Sciences, Guy's, King's and St Thomas's School of Medicine, London SE1 3QD
- 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
- Psychology and Genetics Research Group, King's College London, Guy's Campus, London SE1 9RT
EDITOR—Welton et al found that the proportion of women who were willing to participate in a randomised controlled trial of hormone replacement therapy was higher if participation in a trial without a placebo arm was offered rather than participation in one with a placebo arm, although the difference was of borderline significance.1 Their conclusion was that inclusion of a placebo arm may reduce patients' willingness to participate in a trial. We do not believe that this conclusion is justified.
Allocation of participants to either of the comparison groups was by the woman's choice of appointment time: the nurses offered participation in trials with and without placebo groups in alternate weeks. This is not random allocation, in which only chance can influence which group a participant is allocated to.2 In this …
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