From being almost universally regarded as a methodological virtue of clinical trials and being included in the original 2001 Consolidated Standards of Reporting Trials (CONSORT) statement , measuring the success of blinding has fallen out of fashion. Subsequent versions of CONSORT removed this recommendation based on the correct view that it can lead to misleading inferences about causes of the failure to blind [2,3]. In addition, Anand, et al. recently questioned the need to blind patients and clinicians or measure and report whether blinding was done successfully. While critics are correct to point out problems with the view that blinding is a universal methodological virtue, and to point out that measuring the success of blinding is not straightforward, they are too quick to dismiss the value of testing and reporting on the success of blinding. This is reflected in our findings extending the Template for Intervention Description and Replication (TIDieR) statement for placebo/sham control components, in which almost all Delphi respondents recommended that trials should measure and report whether blinding was successful .
We are not aware of any publications that set out the case for and against measuring blinding success, or that provide mitigating positions. Our experience suggests that confusion about blinding inhibits reasonable debates in this area. Here, we attempt to clarify some of the confusions surrounding blinding and measuring its success, before providing the case for and against, reporting measures of the success of blinding, and suggesting a ‘middle road’ which takes both sides of the debate into account.