PubMed · 10152244
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G D Rubenfeld. 1995. Study design: statistical and methodologic considerations.. https://pubmed.ncbi.nlm.nih.gov/10152244/
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In randomized controlled trials (RCTs), study participants and research personnel are often blinded to minimize biases related to knowing treatment allocation. To determine if blinding was effective, participants may be asked which treatment they believe they received ("treatment guess"). This descriptive review characterized blinding assessment (BA) reporting in pharmacotherapy and neuromodulation neuropathic pain RCTs. Of 288 papers, 36 (12.5%) reported a BA. One paper reported the results of 2 studies, so in total 37 studies with a BA were assessed. Of these, 19 were crossover, 17 parallel, and 1 partial crossover in design. All 37 studies assessed participant blinding, and 10 also assessed investigator blinding. Approximately 27% included an "unsure" answer option for treatment guess, and 38% asked the reason for the guess. There were no clear patterns in BA reporting across time nor based on treatment type. Seventeen trials provided sufficient data to calculate Bang Blinding Index (BI) to determine blinding success. Participants remained blinded (BI = 0 ± 0.2) in 10/17 placebo and 10/17 treatment arms, 6 placebo and 5 treatment arms had a BI > 0.2 suggesting possible unblinding, whereas 1 placebo and 2 treatment arms had a BI < -0.2 suggesting misinformed guessing. Overall, we found that BAs are done in a minority of published neuropathic pain trials and with variable methodology. Given the importance of minimizing risk of bias because of treatment unblinding, future studies should consider including BAs, and further consensus building is necessary to determine if and how BAs should be conducted and interpreted in analgesic clinical trials.
The following procedures are proposed for clinical trials of potentially lethal diseases with a non-fatal primary outcome: (i) comparison of treatments on worst-rank scores combining mortality and the non-fatal outcome; (ii) testing first for mortality differences, and then for differences on the worst-rank scoring if there is no significant evidence for mortality differences. Power and control of type I error rate while testing mortality and worst-rank scores by Bonferroni or closed testing procedures are compared. Used together these procedures improve power to detect treatments with favourable effects on both mortality and the designated non-fatal outcome, while reducing the likelihood of declaring that a treatment benefits patients when undetected adverse effects on mortality are present.
The goal of a screening trial is to examine several treatments with the intention of selecting one or more treatment(s) for further testing. Such a trial frequently occurs in the phase II setting, with the intention that the selected treatment be formally compared to a standard treatment in a phase III clinical trial. In this framework it is not essential that the very best treatment is definitely selected (such a decision would require a formal phase III trial), rather it is important that a substantially inferior treatment is not selected when a superior treatment exists. The level of evidence required to select a treatment based on this standard is lower than the evidence required to definitively order treatments. This paper introduces a flexible design for such trials, the flexibility coming from the use of a particular decision rule. The proposed rule states that if the observed difference in the success rates of the treatments is larger than some prespecified quantity d, then the treatment with the highest observed success rate is selected. However, if the observed difference is less than or equal to d, other factors may be considered in the selection. The goal of this design is to mirror clinical practice, where a treatment's success probability is often only one of many considerations in determining a treatment recommendation for a particular patient.