Background: If a patient agrees to take part in a randomised trial it is reasonable to presume that the patient would prefer to be allocated into the intervention. This study's aim was to investigate how patients react after they have been randomised into control group.
Methods: Nested study within two randomised trials. Telephone interviews with a structured questionnaire. The participants were invited after they had been randomised into the control group in two smoking cessation trials. The main outcome measures were reaction to control group allocation and drop-out rates.
Results: Twenty-seven out of 30 possible interviews were successfully completed. Fourteen persons expressed that they were disappointed of being allocated to the control group. Five persons said that they had not understood the consent information and three of these were very disappointed. Surprisingly these three persons said that they had not expected a randomization. A woman expressed that she "felt as if I was being swindled". There were in total 9/117 (7.7%) lost to follow-up in the control group and there were 4/105 (3.8%) losses to follow-up in the intervention group (P=0.26). Active withdrawal of consent was slightly higher among the control group, five in the control group (4.3%) and no active withdrawals in the intervention group (P=0.06).
Conclusions: Disappointment was common after allocation to the control group. This is a probable explanation of the higher drop-out rate in the control group. The consent information is of highest importance since those who were very disappointed claimed they did not receive understandable information.
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