In this episode, hear from Dr Kate Scrivener, Dr Aidan Cashin and Clinical Associate Professor Mark Elkins about understanding the importance of blinding in trials.

There are numerous stakeholders involved in any clinical trial. These include patients and participants, therapists, researchers, outcome assessors and statisticians.

Stakeholders are a source of bias in trials. This is because they can consciously or subconsciously influence procedures or results based on knowing whether a patient has been allocated to the intervention or control group. To minimise biases, a trial can ‘blind’ the stakeholders to which group participants are allocated. Blinding is considered successful if the stakeholder is unable to distinguish between the treatments applied to the groups.

Three important people or groups to be blinded in clinical trials include the:

1. Patient or participant: where the patient is unaware if they are receiving the intervention or control
2. Therapist: where the therapist is unaware if they are delivering the intervention or control
3. Assessor: where outcome assessor(s) are unaware if the participant being assessed had received the intervention or control

In most physiotherapy trials, it is very difficult to blind participants and therapists. For example, if interventions are physical or active (e.g. exercise), participants will know they are receiving the intervention and therapists will know if they are delivering it. In regard to blinding the assessor, blinding is successful if the assessor does not know which group the patient has been allocated to and outcome measures are objective (e.g. passive range of motion). However, when outcome measures are patient-reported or self-reported (e.g. pain), the assessor is considered blind if the patient was blinded.

Studies frequently report the occurrence of blinding in the title or abstract using terms such as ‘single blinded’ or ‘double blinded’. However, there is inconsistent use of these terms. For example, one ‘double blinded’ trial may have blinded the therapists and outcome assessors, while another may have blinded the patients and statisticians. Readers should investigate which elements of a clinical trial have been blinded and authors should avoid this ambiguous terminology and explicitly state who was blinded.

Some clinical trials attempt to blind patients to their allocated group by providing control interventions that are similar to active interventions. To assess the perceived similarity of the control and active intervention, some studies report the ‘treatment credibility’, where patients are asked ‘How convinced are you that you have received an active therapy?’. Similar treatment credibility between the active and control interventions usually indicates successful blinding.

Many people in a clinical trial can be blinded. Although blinding helps minimise biases, it is often difficult to blind every person. Readers need to assess how a lack of blinding could influence the conduct and reporting of a trial.

In recognition of World Bicycle Day (3 June), Melissa Locke, Rachel Toovey, Claire and Nicholas Draheim (PEDro Education and Training Committee) discuss a randomised controlled trial led by Rachel Toovey about task-specific training for bicycle-riding goals in ambulant children with cerebral palsy.

This episode is part of PEDro's World-Wide Journal Club series.

⁠Toovey RAM, et al. Task-specific training for bicycle-riding goals in ambulant children with cerebral palsy: a randomized controlled trial. Developmental Medicine and Child Neurology 2022 Feb;64(2):243-252⁠

In this episode, we explore a randomised controlled trial led by Rachel Toovey about task-specific training for bicycle-riding goals in ambulant children with cerebral palsy.

Toovey RAM, et al. Task-specific training for bicycle-riding goals in ambulant children with cerebral palsy: a randomized controlled trial. Developmental Medicine and Child Neurology 2022 Feb;64(2):243-252

Dr Tiffany Dwyer from PEDro's Education and Training Committee interviews Prof Linda Denehy about her role in physiotherapy and the future of physiotherapy as part of PEDro's 25th anniversary celebrations.

In this episode we’re joined by Associate Professor Leanne Hassett, Dr Simone Dorsch, Dr Lauren Christie, Reem Rendell, Scott Wade, Emma Fanayan, Roland Qiu and Jenny Yun Jia Qian, as they discuss the EXCITE trial led by Professor Emeritus Steven Wolf as part of the PEDro World-Wide Journal Club Series.

The trial investigated the effect of constraint-induced movement therapy on upper extremity function 3-9 months after stroke. The EXCITE trial is also one of PEDro's Top 25 Trials. These are ground-breaking trials in physiotherapy and were nominated by PEDro users.

Wolf SL, et al. Effect of constraint-induced movement therapy on upper extremity function 3 to 9 months after stroke: the EXCITE randomized clinical trial. JAMA 2006;296(17):2095-104.

In this episode we provide a summary of the EXCITE trial led by Prof Emeritus Steven Wolf as part of the PEDro World-Wide Journal Club series. The trial investigated the effect of constraint-induced movement therapy on upper extremity function 3-9 months after stroke.

The EXCITE trial is also one of PEDro's Top 25 Trials. These are ground-breaking trials in physiotherapy and were nominated by PEDro users.

Wolf SL, et al. Effect of constraint-induced movement therapy on upper extremity function 3 to 9 months after stroke: the EXCITE randomized clinical trial. JAMA 2006;296(17):2095-104.

Dr Tiffany Dwyer from PEDro's Education and Training Committee interviews Prof Jennifer Alison about her role in physiotherapy and the future of physiotherapy as part of PEDro's 25th anniversary celebrations.

In this episode, hear from Dr Kate Scrivener, Dr Aidan Cashin and Clinical Associate Professor Mark Elkins about interpreting comparative effects in trials.

High-quality randomised controlled trials are a great source of evidence to support clinical decisions about which treatment may be best for the patients you work with. When interpreting the findings from trials, it is important to consider both how the outcomes are reported and what the treatment is being compared to.

Trial outcomes are often measured and reported as the ‘within-group’ change in outcomes or as the ‘between-group’ difference in outcomes. The distinction between within-group comparison and between-group comparison is critical when interpreting the results of trials. The between-group difference represents the treatment effect because it does not include natural history, regression to the mean, and nonspecific effects of receiving care which are included in the within-group change.

The treatment effect in trials is always comparative, meaning that the treatment benefit (or harm) is interpreted relative to the other treatment(s) in the trial. This is an important issue because the choice of comparison group will have a big influence on the interpretation of the size of the effect and whether the comparison was a fair test of the treatment.

Choosing the ideal comparison group is not straightforward and is heavily influenced by the research question (spanning the spectrum of efficacy to effectiveness research). For example, guideline-based care may be a suitable comparator if researchers were interested in investigating if the treatment was better than current practice.

The choice of comparison group is also important when trials are synthesised in systematic reviews. It is important that meta-analyses of systematic reviews combine trials with similar treatments, and trials that have similar comparison groups.