If possible, trialists should blind 5 groups of individuals involved in trials: participants, clinicians (surgeons), data collectors, outcome adjudicators and data analysts. If participants are not blinded, knowledge of group assignment may affect their behaviour in the trial and their responses to subjective outcome measures.
Is it possible to blind study participants and intervention agents?
Although it is often impossible to blind study participants and intervention agents, the blinding of data collectors, data analysts, and nonresearch healthcare staff should be pursued. Practical tips for surgical research: blinding: who, what, when, why, how?
What is the purpose of blinding in clinical trials?
After randomization, blinding (also called "masking") is used to guard against a placebo effect and/or biased outcome assessment. It is most important for the primary outcome to be measured and recorded objectively, without knowledge of the actual treatment assignment.
How should the assignment of treatment be concealed in randomized trials?
Whenever feasible, randomized trials should incorporate mechanisms for safeguarding the identity of the treatment assignment from investigators, study staff, and participants. In traditional individually randomized trials, the assignment is concealed from the investigators before randomization to protect against treatment selection bias.
Should medical staff care for patients in a randomised trial be blinded?
Similarly, medical staff caring for patients in a randomised trial should be blinded to treatment allocation to minimise possible bias in patient management and in assessing disease status.
What is the purpose of blinding in clinical trials?
Blinding (sometimes called masking) is used to try to eliminate such bias. It is a tenet of randomised controlled trials that the treatment allocation for each patient is not revealed until the patient has irrevocably been entered into the trial, to avoid selection bias.
Why would it be important for the outcome assessors to be blinded to treatment allocation in an open label trial?
The goal of blinded outcome assessment is to ensure that bias is not introduced due to knowledge of the patient's treatment group. However, blinded outcome assessment alone is not sufficient to prevent bias; it is also necessary to ensure that the information upon which the assessment is based is not subject to bias.
What is blinding and what is its purpose?
Blinding refers to covering up of certain information from one or more research participants in a clinical research study, most commonly a Randomized Controlled Trial (RCT) to reduce bias. Blinding is mainly carried out while conducting RCTs.
Why is blinding important in systematic review?
This is important because if the researcher is aware of certain study characteristics (e.g. what journal the study was published in) they may inadvertently assess the study a certain way. For example, if the author of the study is well-known to the assessor, they may be more likely to assume it is of 'high quality'.
What does blinding of outcome assessment mean?
Blind outcome assessment refers to the process of concealing treatment group identity from outcome assessors, after their treatment assignment through randomization, to minimize the occurrence of biased assessments influencing research findings.
How do blind experiments increase the validity of research results?
Blinding is important to reduce bias (e.g., observer bias, demand characteristics) and ensure a study's internal validity. If participants know whether they are in a control or treatment group, they may adjust their behavior in ways that affect the outcome that researchers are trying to measure.
Why is it important to blind participants in a study?
Blinding is an important methodologic feature of RCTs to minimize bias and maximize the validity of the results. Researchers should strive to blind participants, surgeons, other practitioners, data collectors, outcome adjudicators, data analysts and any other individuals involved in the trial.
What is a blinding method?
Blinding is a procedure in which one or more parties in a trial are kept unaware of which treatment arms participants have been assigned to, in other words, which treatment was received.
Does blinding reduce performance bias?
Blinding of participants and personnel reduces performance bias. A patient or practitioner who trusts in the effect of a specific intervention may unconsciously or intentionally perceive or detect an enhanced treatment effect [4].
What’s the difference between method and methodology?
Methodology refers to the overarching strategy and rationale of your research project . It involves studying the methods used in your field and...
What’s the difference between quantitative and qualitative methods?
Quantitative research deals with numbers and statistics, while qualitative research deals with words and meanings. Quantitative methods allow yo...
What is sampling?
A sample is a subset of individuals from a larger population . Sampling means selecting the group that you will actually collect data from in...
What’s the difference between reliability and validity?
Reliability and validity are both about how well a method measures something: Reliability refers to the consistency of a measure (whether the r...
What is the difference between internal and external validity?
I nternal validity is the degree of confidence that the causal relationship you are testing is not influenced by other factors or variables . Ext...
What is experimental design?
Experimental design means planning a set of procedures to investigate a relationship between variables . To design a controlled experiment, you ne...
What are independent and dependent variables?
You can think of independent and dependent variables in terms of cause and effect: an independent variable is the variable you think is the ca...
What is the difference between quantitative and categorical variables?
Quantitative variables are any variables where the data represent amounts (e.g. height, weight, or age). Categorical variables are any variables...
What is the difference between discrete and continuous variables?
Discrete and continuous variables are two types of quantitative variables : Discrete variables represent counts (e.g. the number of objects in a...
Why is blinding important?
Blinding is important to reduce bias and ensure a study’s internal validity. If participants know whether they are in a control or treatment group, they may adjust their behavior in ways that affect the outcome that researchers are trying to measure.
Why is it important to include mediators in research?
Including mediators and moderators in your research helps you go beyond studying a simple relationship between two variables for a fuller picture of the real world. They are important to consider when studying complex correlational or causal relationships.
Can a factorial design be combined?
Yes. Between-subjects and within-subjects designs can be combined in a single study when you have two or more independent variables (a factorial design). In a mixed factorial design, one variable is altered between subjects and another is altered within subjects.
What is the most common method of blinding in RCTs?
One of the most common methods of blinding in RCTs is the use of seemingly identical medications; one ‘active’ pill and one ‘placebo’ pill. As they are physically identical, it is impossible for patients and researchers to discern which pill is the active one based on appearance alone.
What happens if the clinician knows a particular patient that they think will be good for the experimental drug group?
Similarly, if the clinician knows a particular patient that they think will be ‘good’ for the experimental drug group, and the allocation sequence is known , they may ‘skip’ the prior patients so that the patient they want is assigned to the experimental drug.
What is allocation concealment?
Allocation concealment is ensuring that the person (s) randomising participants does not know what the next treatment allocation must be. This is an often underappreciated aspect of many trials that may lead to significant selection bias and invalid conclusions if not implemented [6,7].
Is blinding possible?
In cases where blinding is not possible or feasible, the outcome measures must be objective! If you are reading a study that is un-blinded, with subjective outcome measures, then you may as well stop reading it and move on.
Should blinding be attempted in other areas of the study?
It is recommended that the groups are treated as equally as possible, blinding should be attempted in other areas of the study and that any lack of blinding should be recognised in the limitations section [8].
Can a surgeon be blinded?
However, it can be difficult to blind the surgeon to the tested intervention as they must perform the procedure. This still remains a challenge in medical research. (Although it is not impossible to blind surgeons: have a look at this for more information).
Should RCTs be double blind?
Where possible, RCTs should be at least double-blinded, and should have more blinding where possible (this includes: patients, clinicians/researchers, data collectors and statisticians) Where blinding is not feasible, this should be recognised as a limitation and blinding should be attempted in other areas of the trial.
What is blinding in clinical trials?
Blinding or masking (the process of keeping the study group assignment hidden after allocation) is commonly used to reduce the risk of bias in clinical trials with two or more study groups. 166; 248 Awareness of the intervention assigned to participants can introduce ascertainment bias in the measurement of outcomes, particularly subjective ones (e.g., quality of life) 166;167; performance bias in the decision to discontinue or modify study interventions (e.g., dosing changes) ( Item 11b ), concomitant interventions, or other aspects of care ( Item 11d) 229; and exclusion/attrition bias in the decision to withdraw from the trial or to exclude a participant from the analysis. 249;250 We have elected to use the term “blinding”, but acknowledge that others prefer the term “masking” because “blind” also relates to an ophthalmologic condition and health outcome. 251;252
Is blinding a protocol?
Despite its importance, blinding is often poorly described in trial protocols. 3 The protocol should explicitly state who will be blinded to intervention groups – at a minimum, the blinding status of trial participants, care providers, and outcome assessors.
Why is blinding important in epidemiology?
Blinding is important in other types of research too. For example, in studies to evaluate the performance of a diagnostic test those perform ing the test must be unaware of the true diagnosis.
What is blinding in a trial?
It is a tenet of randomised controlled trials that the treatment allocation for each patient is not revealed until the patient has irrevocably been entered into the trial, to avoid selection bias.
What is double blinding in clinical trials?
In controlled trials the term blinding, and in particular “double blind,” usually refers to keeping study participants, those involved with their management, and those collecting and analysing clinical data unaware of the assigned treatment, so that they should not be influenced by that knowledge.
Should cases be kept secret?
In epidemiological studies it is preferable that the identification of “cases” as opposed to “controls” be kept secret while researchers are determining each subject's exposure to potential risk factors.
Can patients see the treatment being given to patients in the other treatment group?
Patients may well see the treatment being given to patients in the other treatment group (s), and the appearance of the drug used in the study could give a clue to its identity. Differences in taste, smell, or mode of delivery may also influence efficacy, so these aspects should be identical for each treatment group.
Is blinding always possible?
Blinding is certainly not always easy or possible. Single blind trials (where either only the investigator or only the patient is blind to the allocation) are sometimes unavoidable, as are open (non-blind) trials. In trials of different styles of patient management, surgical procedures, or alternative therapies, full blinding is often impossible.
Why is the assignment hidden in a randomized trial?
In traditional individually randomized trials, the assignment is concealed from the investigators before randomization to protect against treatment selection bias. For example, in an individually randomized trial, a provider may be biased to believe that one of the “treatments” would not be good for elderly patients.
Why is blinding important?
It is most important for the primary outcome to be measured and recorded objectively, without knowledge of the actual treatment assignment.
Why is concealment not an issue in CRTs?
With CRTs, concealment is not usually an issue because all of the clusters are identified ahead of time and are randomized at the same time. Hence, unlike individually randomized trials in which participants enter the study over time, there is no opportunity to “predict” the assignment and alter behavior accordingly.
Why is blinding used in research?
Blinding prevents ascertainment bias and protects the sequence after allocation. 3, 4 By contrast, researchers use methods of allocation concealment primarily to prevent selection bias and to protect an assignment sequence before and until allocation. Furthermore, in some trials, blinding cannot be successfully implemented, ...
What is blinding in a controlled trial?
Blinding represents an important, distinct aspect of randomised controlled trials. 3 The term blinding refers to keeping trial participants, investigators (usually healthcare providers), or assessors (those collecting outcome data) unaware of an assigned intervention, so that they are not influenced by that knowledge.
What is blinding in health care?
The term blinding refers to keeping trial participants, investigators (usually health-care providers), or assessors (those collecting outcome data) unaware of the assigned intervention, so that they will not be influenced by that knowledge.
What is the difference between blinding and non blinding?
Lexicon of blinding. Non-blinded (open or open label) denotes trials in which everyone involved knows who has received which interventions throughout the trial. Blinding (masking) indicates that knowledge of the intervention assignments is hidden from participants , trial investigators , or assessors.
Why is blinding less important?
In general, though, blinding becomes less important to reduce observer bias as the outcomes become less subjective, since objective (hard) outcomes leave little opportunity for bias. Knowledge of the intervention would not greatly affect measurement of a hard outcome, such as death.
What does quadruple blind mean?
11 Thus, quintuple blind must mean that the allocation schedule has been lost and nobody knows anything.
What is triple blind trial?
Triple blind usually means a double-blind trial that also maintains a blind data analysis. 10 Some investigators, however, denote trials as triple-blind if investigators and assessors are distinct people and both, as well as participants, remain unaware of assignments.
What Is Blinding?
Common Methods of Blinding
- One of the most common methods of blinding in RCTs is the use of seemingly identical medications; one ‘active’ pill and one ‘placebo’ pill. As they are physically identical, it is impossible for patients and researchers to discern which pill is the active one based on appearance alone. This is an example of robust blinding. If it is not robust, there is a risk of un-blinding. This is dem…
Why Is Blinding Important?
- Blinding is important for the validity of RCTs. Without it there are number of biases that are unwillingly introduced.It has been shown in an assessment of 33 meta-analyses, encompassing 250 RCTs, that without blinding, odds ratios were exaggerated by up to 17% (P=0.01). This highlights the importance of not just reading medical literature, but app...
What About When Blinding Is Not Possible?
- In cases where blinding is not possible or feasible, the outcome measures must be objective!If you are reading a study that is un-blinded, with subjective outcome measures, then you may as well stop reading it and move on. This is because, if a patient is aware they are receiving the active intervention and the outcome measure is subjective, such as ‘how much pain they are exp…
Allocation Concealment
- Allocation concealment is ensuring that the person(s) randomising participants does not know what the next treatment allocation must be. This is an often underappreciated aspect of many trials that may lead to significant selection bias and invalid conclusions if not implemented[6,7]. CONSORT guidelines recommend that all RCTs have a robust method of randomisation to ensur…
Summary
- Blinding is an important foundation for ensuring internal validity and reducing observer bias
- Blinding must be robust and methods of blinding should be reported in detail
- Where possible, RCTs should be at least double-blinded, and should have more blinding where possible (this includes: patients, clinicians/researchers, data collectors and statisticians)
- Where blinding is not feasible, this should be recognised as a limitation and blinding should b…
- Blinding is an important foundation for ensuring internal validity and reducing observer bias
- Blinding must be robust and methods of blinding should be reported in detail
- Where possible, RCTs should be at least double-blinded, and should have more blinding where possible (this includes: patients, clinicians/researchers, data collectors and statisticians)
- Where blinding is not feasible, this should be recognised as a limitation and blinding should be attempted in other areas of the trial
