Related Experiment Video
Updated: Jul 17, 2026
04:11
A Video Protocol of a Randomized Controlled Clinical Trial - Electrochemotherapy of Cutaneous Metastases with Reduced Dose Bleomycin (BLESS Trial)
Published on: June 9, 2026
Evaluating blinding in trials of endometrial scratching: a randomised nested survey within two randomised controlled
Sarah Lensen1, Afsana Afroz2, Lynn Sadler3
1Department of Obstetrics, Gynaecology and Newborn Health, University of Melbourne, Royal Women's Hospital, Melbourne, Australia. sarah.lensen@unimelb.edu.au.
Trials
|July 16, 2026
Summary
Participant blinding in physical procedure trials, like endometrial scratching, is often ineffective. While participants could guess their treatment, this did not impact key trial behaviors like intercourse frequency.
Area of Science:
- Reproductive Medicine
- Clinical Trial Methodology
- Evidence-Based Medicine
Background:
- Blinding in randomized controlled trials (RCTs) minimizes bias but is challenging to maintain.
- Participants may discern their treatment allocation through side effects or procedural experiences.
- Formal tools like the James and Bang blinding indices assess the effectiveness of blinding.
Purpose of the Study:
- To evaluate the effectiveness of participant blinding in RCTs involving physical procedures, using endometrial scratching as a case study.
- To determine if procedural symptoms (pain, bleeding) and participant behaviors (intercourse patterns, protocol violations) correlate with unblinding.
- To assess the impact of unblinding on crucial trial outcomes.
Main Methods:
- A randomized survey assessed participant ability to guess their allocation in endometrial scratching trials.
- Participants guessed allocation early or late in the trial.
- Blinding was evaluated using Bang's and James' blinding indices; associations with symptoms and behaviors were analyzed using chi-squared and t-tests.
Main Results:
- 56% of participants correctly guessed their trial allocation.
- Pain and bleeding were higher in the endometrial scratching group and associated with correct guessing.
- Blinding indices indicated a lack of effective blinding, particularly in the intervention group.
Conclusions:
- The sham procedure in endometrial scratching trials did not ensure complete participant blinding.
- Despite a lack of blinding, no evidence suggested impacts on important trial behaviors like intercourse frequency.
- Further research may be needed to optimize blinding in trials involving physical interventions.
Related Concept Videos
01:11Blinding
Blinding is a commonly used method of not telling participants which treatment a subject is receiving. Blinding is a critical part of a randomized control trial or RCT. It reduces the bias that affects the results. In an RCT, blinding is used in the form of a placebo. A placebo effect occurs when untreated subjects falsely believe they have received the treatment and report improved symptoms. A placebo or a dummy treatment is administered to subjects to negate the bias caused by such an effect.
02:07Blind Procedures
Ideally, the people who observe and record the children’s behavior are unaware of who was assigned to the experimental or control group, in order to control for experimenter bias. Experimenter bias refers to the possibility that a researcher’s expectations might skew the results of the study. Remember, conducting an experiment requires a lot of planning, and the people involved in the research project have a vested interest in supporting their hypotheses. If the observers knew which child was...
01:23Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches
Biopharmaceutical studies constitute a vital field aiming to enhance drug delivery methods and refine therapeutic approaches, drawing upon diverse interdisciplinary knowledge. In research methodologies, the choice between controlled and non-controlled studies significantly influences the study's reliability and accuracy.
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
01:15Bioequivalence Experimental Study Designs: Repeated Measures, Cross-Over, Carry-Over, and Latin Square Designs
Bioequivalence experimental study designs play a pivotal role in testing the effectiveness of various treatments. Key among these are the repeated measures, cross-over, carry-over, and Latin square designs. In the repeated measures design, each subject receives all treatments, allowing for temporal comparisons. This type of design is useful in reducing variability but requires careful planning to avoid bias.The cross-over design, an economical method, involves sequential administration of...
01:25Strategies for Assessing and Addressing Confounding
Confounding is a critical issue in epidemiological studies, often leading to misleading conclusions about associations between exposures and outcomes. It occurs when the relationship between the exposure and the outcome is mixed with the effects of other factors that influence the outcome. Given that, addressing confounding is of high importance for drawing accurate inferences in research.
Confounding can be addressed at both the design phase of a study and through analytical methods after data...
Confounding can be addressed at both the design phase of a study and through analytical methods after data...
01:13Randomized Experiments
The randomization process involves assigning study participants randomly to experimental or control groups based on their probability of being equally assigned. Randomization is meant to eliminate selection bias and balance known and unknown confounding factors so that the control group is similar to the treatment group as much as possible. A computer program and a random number generator can be used to assign participants to groups in a way that minimizes bias.
Simple randomization
Simple...
Simple randomization
Simple...