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Non-standard and preference designs
Published in David A. Richards, Ingalill Rahm Hallberg, Complex Interventions in Health, 2015
A further design taking preferences into account is the two-stage randomized design, the so-called Rücker or Wennberg design (Rücker, 1989; Wennberg et al., 1993). The design is useful to estimate direct intervention effects, as well as preference and selection effects. Participants are initially randomized to two groups to reduce baseline imbalances between randomized and preference groups. One group is then offered a choice of intervention in the same way as the preference groups in a comprehensive cohort design. The other group is randomized as in an RCT. In the Rücker design, participants randomized to the preference group in the first randomization and who do not have a strong preference for an intervention are randomized a second time to an intervention. These designs offer a more powerful method of determining the influence of preference on outcome than the CCD, in which preferences are not evenly distributed between groups within the preference arm because participants are free to choose which group they will join. The design overcomes the ethical problem created by the Zelen design in that consent is achieved prior to randomization. However, the design does not circumvent the difficulty of recruiting those who have such strong preferences that they are not prepared to risk the first randomization. See Box 21.1 for a summary of the internal and external validity and study administration of the design. McCafferey and colleagues (2011) used the Rücker method to understand the effect of patient choice on patient outcomes in a trial of management strategies for women with atypical cells of undetermined significance detected at routine cervical screening. Women were randomized to either an informed choice of human papillomavirus triage testing or to repeat pap testing or to no choice with random allocation to management by either option.
Use of pre-enrollment randomization and delayed consent to maximize participation in a clinical trial of opt-in versus opt-out tobacco treatment
Published in Substance Abuse, 2022
Babalola Faseru, Laura M. Mussulman, Niaman Nazir, Edward F. Ellerbeck, Elena Shergina, Taneisha S. Scheuermann, Byron J. Gajewski, Delwyn Catley, Kimber P. Richter
The Zelen’s design was originally proposed in 1979 as a pragmatic research design6 in which patients are consented after randomization. It can markedly enhance recruitment and improve generalizability by including a higher proportion of eligible patients.7,8 For example, in a four-site trial in which one site consented patients after randomization and three sites used “normal” consent, the sites that used the Zelen’s design recruited 86% of eligible participants; the other sites recruited 19%, 26%, and 52%, respectively.7 Accordingly, Zelen’s procedure has been used in trials to provide a more accurate estimate of the effects of an intervention when implemented on a population basis.8 These interventions include care navigation to prevent suicide attempts or self-harm,9,10 ehealth intervention for eating disorders,11 text messaging intervention for HIV prevention,12 rehabilitation interventions,13,14 health coaching for chronic disease management,15 interventions to prevent childhood dental caries,16 prevention of rehospitalization and use of emergency department.17 The current study is the first to use the Zelen’s design in smoking cessation trial.18
Nocebo effects and psychotropic drug action - an update
Published in Expert Review of Clinical Pharmacology, 2020
1) A further natural history group (NH), the so-called ‘third arm’ of the experimentation, should be added and considered, in order to better study the side effects usually observed in the placebo group, in terms of nocebo effects. This third group would make it possible to study adverse events more accurately, such as the difference between the symptoms collected in the NH group and the side effects presented in the placebo group [11]. As previously noted, the observations achieved through the NH group analysis should be incorporated more frequently into the RCTs, such as in Zelen Design. This would allow monitoring the NH of AEs without randomizing patients into a ‘no treatment’ control group in order to overcome ethical issues.