Explain A Situation When A Double-Blind Study Is Not Possible?

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Explain A Situation When A Double-Blind Study Is Not Possible
A Closer Look at Double-Blind Studies – Let’s take a closer look at what we mean by a double-blind study and how this type of procedure works. As mentioned previously, double-blind indicates that the participants and the experimenters are unaware of who is receiving the real treatment.

  1. What exactly do we mean by ‘treatment’? In a psychology experiment, the treatment is the level of the independent variable that the experimenters are manipulating.
  2. This can be contrasted with a single-blind study in which the experimenters are aware of which participants are receiving the treatment while the participants remain unaware.

In such studies, researchers may use what is known as a placebo. A placebo is an inert substance, such as a sugar pill, that has no effect on the individual taking it. The placebo pill is given to participants who are randomly assigned to the control group.

  • A control group is a subset of participants who are not exposed to any levels of the independent variable,
  • This group serves as a baseline to determine if exposure to the independent variable had any significant effects.
  • Those randomly assigned to the experimental group are given the treatment in question.

Data collected from both groups are then compared to determine if the treatment had some impact on the dependent variable, All participants in the study will take a pill, but only some of them will receive the real drug under investigation. The rest of the subjects will receive an inactive placebo.
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Why will it be impossible to conduct a double-blind experiment?

Statistics Notes: Blinding in clinical trials and other studies Human behaviour is influenced by what we know or believe. In research there is a particular risk of expectation influencing findings, most obviously when there is some subjectivity in assessment, leading to biased results.

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. This sort of blinding, better referred to as allocation concealment, will be discussed in a future statistics note.

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.

The relevance of blinding will vary according to circumstances. Blinding patients to the treatment they have received in a controlled trial is particularly important when the response criteria are subjective, such as alleviation of pain, but less important for objective criteria, such as death. 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.

For example, the decision to withdraw a patient from a study or to adjust the dose of medication could easily be influenced by knowledge of which treatment group the patient has been assigned to. In a double blind trial neither the patient nor the caregivers are aware of the treatment assignment.

Blinding means more than just keeping the name of the treatment hidden. 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.

Even colour of medication has been shown to influence efficacy. In studies comparing two active compounds, blinding is possible using the “double dummy” method. For example, if we want to compare two medicines, one presented as green tablets and one as pink capsules, we could also supply green placebo tablets and pink placebo capsules so that both groups of patients would take one green tablet and one pink capsule.

  1. Blinding is certainly not always easy or possible.
  2. 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.
  3. In trials of different styles of patient management, surgical procedures, or alternative therapies, full blinding is often impossible.

In a double blind trial it is implicit that the assessment of patient outcome is done in ignorance of the treatment received. Such blind assessment of outcome can often also be achieved in trials which are open (non-blinded). For example, lesions can be photographed before and after treatment and assessed by someone not involved in running the trial.

Indeed, blind assessment of outcome may be more important than blinding the administration of the treatment, especially when the outcome measure involves subjectivity. Despite the best intentions, some treatments have unintended effects that are so specific that their occurrence will inevitably identify the treatment received to both the patient and the medical staff.

Blind assessment of outcome is especially useful when this is a risk. 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.

  1. In many such studies blinding is impossible because exposure can be discovered only by interviewing the study participants, who obviously know whether or not they are a case.
  2. The risk of differential recall of important disease related events between cases and controls must then be recognised and if possible investigated.

As a minimum the sensitivity of the results to differential recall should be considered. Blinded assessment of patient outcome may also be valuable in other epidemiological studies, such as cohort studies. Blinding is important in other types of research too.

For example, in studies to evaluate the performance of a diagnostic test those performing the test must be unaware of the true diagnosis. In studies to evaluate the reproducibility of a measurement technique the observers must be unaware of their previous measurement(s) on the same individual. We have emphasised the risks of bias if adequate blinding is not used.

This may seem to be challenging the integrity of researchers and patients, but bias associated with knowing the treatment is often subconscious. On average, randomised trials that have not used appropriate levels of blinding show larger treatment effects than blinded studies.

Similarly, diagnostic test performance is overestimated when the reference test is interpreted with knowledge of the test result. Blinding makes it difficult to bias results intentionally or unintentionally and so helps ensure the credibility of study conclusions.1. De Craen AJM, Roos PJ, de Vries AL, Kleijnen J.

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Effect of colour of drugs: systematic review of perceived effect of drugs and their effectiveness. BMJ.1996; 313 :1624–1626.2. Barry D. Differential recall bias and spurious associations in case/control studies. Stat Med.1996; 15 :2603–2616.3. Schulz KF, Chalmers I, Hayes R, Altman DG.

  • Empirical evidence of bias: dimensions of methodological quality associated with estimates of treatment effects in controlled trials.
  • JAMA.1995; 273 :408–412.4.
  • Lijmer JG, Mol BW, Heisterkamp S, Bonsel GJ, Prins MH, van der Meulen JH, et al.
  • Empirical evidence of design-related bias in studies of diagnostic tests.

JAMA.1999; 282 :1061–1066.
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Are double-blind studies always possible?

Issues of Concern – Blinding covers any of the numerous participants of the clinical trial, e.g., researchers, subjects, technicians, and data analysts. Single-, double-, and triple-blinding are commonly used blinding strategies in clinical research. A single-blind study masks the subjects from knowing which study treatment, if any, they are receiving.

A double-blind study blinds both the subjects as well as the researchers to the treatment allocation. Triple-blinding involves withholding this information from the patients, researchers, as well as data analysts.Randomized, double-blind placebo-controlled trials involve the random placement of participants into two groups; an experimental group that receives the investigational treatment and a control group that acquires a placebo.

Neither the researchers nor the study subjects know who is getting the experimental treatment and who is getting a placebo. This type of clinical study ranks as the gold standard for the validation of treatment interventions. Unfortunately, blinding is not possible to achieve in all clinical trials.
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What is a difficulty with double-blind experiments in psychology?

1. It is expensive – One huge disadvantage of a double-blind study is that it is expensive to conduct. It takes several months or years to complete because the researcher has to examine all the possible variables and they may have to use different groups to gather enough data.
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What happens when there is no blinding in a study?

Who should I blind? – Differential treatment or assessment of participants potentially resulting in bias may occur at any phase of a trial. 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. For example, a participant who is aware that he is not receiving active treatment may be less likely to comply with the trial protocol, more likely to seek additional treatment outside of the trial and more likely to leave the trial without providing outcome data.

Those aware that they are receiving or not receiving therapy are more likely to provide biased assessments of the effectiveness of the intervention — most likely in opposite directions — than blinded participants.7 Similarly, blinded clinicians are much less likely to transfer their attitudes to participants or to provide differential treatment to the active and placebo groups than are unblinded clinicians.7 Blinding of data collectors and outcome adjudicators (sometimes the same individuals) is crucial to ensure unbiased ascertainment of outcomes.

For example, in a randomized controlled trial of cyclophosphamide and plasma exchange in patients with multiple sclerosis, neither active treatment regimen was superior to placebo when assessed by blinded neurologists, but there was an apparent benefit of treatment with cyclophosphamide, plasma exchange and prednisone when unblinded neurologists performed the assessments.8 Although subjective outcomes are most at risk of ascertainment bias, seemingly objective outcomes often require some degree of subjectivity and therefore are at risk of bias as well.

Bias may also be introduced during the statistical analysis of the trial through the selective use and reporting of statistical tests. This may be a subconscious process spurred by investigators eager to see a positive result, but the consequences are profound.

The best method to avoid this potential bias is blinding of the data analyst until the entire analysis has been completed. This rationale strongly suggests that the blinding of as many individuals as is practically possible limits bias in clinical trials. In the past, many researchers have referred to trials that blinded several groups of individuals as “double-blind.” This term is ambiguous, inconsistently applied, and has different meanings to different individuals.9 Blinding is not an all-or-nothing phenomenon; researchers may blind any of the involved groups.

Furthermore, even within one of the groups (such as outcome adjudicators), some individuals may be blinded while others are aware of group allocation. Thus, it is far preferable for researchers to explicitly state which individuals in the trial were blinded, how they achieved blinding and whether they tested the successfulness of blinding.
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Is it impossible to conduct a double-blind study of whether psychotherapy is effective?

Conclusions – The conclusions of the rationale presented in this paper would be that for MDD:

  • 1. Pill placebos show considerable positive effect on disorders with subjective endpoints such as those used to rate MDD 5 – 7,
  • 2. Psychological placebos may be as effective as accepted psychotherapies 11,
  • 3. Psychotherapy clinical trials are non-blinded studies, and cannot effectively be double-blinded. Calling these studies “single-blind” obfuscates the non-blinded nature of these studies and is not in line with the definition of “single-blind” in a clinical trial 4,
  • 4. It is imperative that any intervention for a disorder with subjective endpoints such as MDD requires the same rigor in double-blinding in order to conclude that the results show “efficacy” or are “evidence-based”. This paper proposes to use the term, “partially-controlled clinical data” in place of “evidence-based clinical data” for results obtained from unblinded studies.

The implications for practice are, 1. For practitioners to be clear with patients the level of rigor to which interventions have been studied, 2. For authors of psychotherapy outcome studies to be clear that the problem in the inability to blind a psychotherapy trial severely restricts the validity of any conclusions that can be drawn, and 3.

To petition National Health Insurance Plans to use caution in approving interventions studied without double-blinded confirmatory trials as they may lead patients to avoid other treatments shown to be effective in double-blinded trials. The limitations of this paper are that the lack of double-blinding does also not prove that the psychotherapy intervention is not helpful in some way to the indication being treated.

Clinical opinion and consensus may guide how a psychotherapy will be used in practice. We hope this paper can stimulate more research related to problems in blinding of psychotherapy outcome studies, the potential economic and clinical costs of providing or not-providing private or national health reimbursement for psychotherapeutic interventions, and further discussion on how our official professional organizations and national research centers will define “evidence-based” in relation to interventions for major depressive disorder.
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Which of the following is a weakness of a double-blind clinical trial?

One weakness of a double-blind clinical trial is the inability to test some research questions due to ethical concerns.
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Who is not blinded in a double-blind study?

A type of clinical trial in which neither the participants nor the researcher knows which treatment or intervention participants are receiving until the clinical trial is over.
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How do you know if an experiment can be double-blind?

A double-blind study occurs when neither the participants nor the researchers involved in a study know who’s been assigned to the control and treatment groups.
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Are double-blind experiments reliable?

When drugs or vaccines are being trialed for their effectiveness, there are typically several stages. Double-blind trials are seen as the most reliable type of study because they involve neither the participant nor the doctor knowing who has received what treatment. The aim of this is to minimize the placebo effect and minimize bias. Explain A Situation When A Double-Blind Study Is Not Possible Image Credit: AllaBond/Shutterstock.com
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What kind of bias does a double-blind study limit?

Background – The aim of evidence-based medicine is to find the optimal treatment for patients. This process is based on the expertise of the treating practitioner, the characteristics of patients and the best available external evidence, If available, the best external evidence is data from proper conducted randomized controlled trials (RCT), Properly conducted RCT take several measures to minimize bias in order to get valid conclusions, Bias describes a systematic error which leads to deviation of the measured effect away from the true effect of an intervention, The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org. (Accessed 01 Nov 2015)” href=”https://localhost/articles/10.1186/s13643-016-0226-4#ref-CR4″ id=”ref-link-section-d137713439e547″>4 ]. The Cochrane Collaboration defined the following standard domains of bias: random sequence generation, allocation sequence concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective outcome reporting and others. These domains are part of critical appraisal in order to judge validity of trials. Influence of bias on quantitative results can be revealed when conducting sensitivity analyses, The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org. (Accessed 01 Nov 2015)” href=”https://localhost/articles/10.1186/s13643-016-0226-4#ref-CR4″ id=”ref-link-section-d137713439e550″>4 ]. The CONSORT statement (Consolidated Standards of Reporting Trials), a guideline on reporting of outcomes in randomized controlled trials, declared the information to evaluate these domains of bias as mandatory, One measure to reduce bias is blinding. The risk that awareness of the applied intervention bias effects is called 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, The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org. (Accessed 01 Nov 2015)” href=”https://localhost/articles/10.1186/s13643-016-0226-4#ref-CR4″ id=”ref-link-section-d137713439e559″>4 ]. The common term “double-blinded” refers to full avoidance of performance bias by blinding both participants and personnel, Detection bias refers to the risk of how the evaluation of the outcome bias effects. Blinding of outcome assessors reduces detection bias. Outcome assessors (study nurses or investigators) who are aware of the actual treatment may unconsciously or intentionally alter their assessment. Particularly, in case of soft endpoints, e.g. pain blinding of outcome assessors is important. For hard comparators like mortality detection bias is irrelevant, The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org. (Accessed 01 Nov 2015)” href=”https://localhost/articles/10.1186/s13643-016-0226-4#ref-CR4″ id=”ref-link-section-d137713439e565″>4, 7 ]. To express bias quantitatively, the association of lack of blinding and significant results is expressed as an odds ratio. From other medical disciplines, four empirical studies exist on this topic. Each of them compared the results of clinical trials with absent versus present blinding. A meta-analysis of these empirical studies showed an odds ratio of 0.86 (95 % confidence interval 0.74 to 0.99) demonstrating that lack of blinding leads to overestimated treatment effects, Similarly, the degree of detection bias has been investigated. Blinded and unblinded neurologists assessed a medical intervention to treat multiple sclerosis. Although, no treatment benefit was present, the unblinded neurologists’ scores demonstrated an apparent treatment benefit whereas the blinded neurologists’ scores did not, Due to the physical component of interventions, surgical RCT methodology has some specifics. Blinding of the operating surgeon is sometimes impossible. Blinding of patients and outcome assessors is not easily applicable, The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org. (Accessed 01 Nov 2015)” href=”https://localhost/articles/10.1186/s13643-016-0226-4#ref-CR4″ id=”ref-link-section-d137713439e593″>4, 13 ]. For several non-pharmacological treatments, different blinding methods have been investigated, providing detailed methodological information about possible extent of blinding in surgery, However, it remains unclear if ornate blinding measures for surgical interventions are really justified by the gain of better evidence. Cancelling out the blinding measures of patients due to the physical component is very probable and has never been systematically investigated. Until today, influence of detection and performance bias in general and abdominal surgery RCT is unexplored. The objective of the planned systematic review and empirical study is to investigate actual impact on outcomes and future potential of blinding in general and abdominal surgery RCT.
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What is the opposite of a double-blind experiment?

A type of study in which the patients (single-blinded) or the patients and their doctors (double-blinded) do not know which drug or treatment is being given. The opposite of a blinded study is an open label study.
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When would you use a double-blind study?

Double blind studies prevent bias when doctors evaluate patients’ outcomes. This improves reliability of clinical trial results. Should you have health complications during a trial, such as a possible drug reaction, your doctor can ‘unblind’ you and find out which treatment you’re receiving.
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What bias is caused by not blinding?

Impact – Quantitative evidence demonstrates that blinding in clinical trials affects the results reported: Schulz and coworkers analysed data from 250 randomized controlled trials which had been included in 33 studies, to give an overall effect estimate,” data-getit_link=”” title=”Click to view the GET-IT definition of this term”>meta-analyses, Studies that did not report double-blinding showed on average odds ratios that were 17% higher than studies that did not. Objective outcomes, such as death are less at risk of bias from lack of blinding, particularly outcome assessors. Trials with subjective outcomes (those based on feelings such as pain, rather than objectively measured outcomes such as diagnostic records) might be more at risk of bias from lack of blinding. For example, osteoarthritis trials tend to use patient-reported pain and function outcomes. A study looking at the influence of lack of blinding in 122 trials including 27,452 participants found that estimated treatment effects were smaller for trials with adequate blinding compared with trials with inadequate blinding. A systematic review of meta-analyses looked at the average bias and heterogeneity associated with reported methodological aspects of randomized controlled trials: “Lack of/unclear double blinding (versus double blinding, where both participants and personnel/assessors are blinded) was associated with a 23% exaggeration of intervention effect estimates in trials with subjective outcomes (ROR 0.77, 95% CI 0.61 to 0.93). In contrast, there was little evidence of such bias in trials of mortality or other objective outcomes, or when all outcomes were analysed (ROR 0.92, 95% CI 0.74 to 1.14;I2 33%).”
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What are the consequences of collecting data blindly?

Prioritization becomes harder – Moreover, collecting blindly without establishing a goal beforehand, will complicate the differentiation between valuable and dispensable data. The more ‘noise’, the bigger the risk of mismatched messages or services. After all, when you collect information endlessly, it will become increasingly difficult to understand what is truly important to your customer.
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What is the disadvantage of double-blind peer review?

Disadvantages of double-blind review – The biggest argument is that double-blind peer reviewing is not really blind after all. With some research sectors being so small, it is very easy to have an educated guess of who the author is. When an author is trying to make a point in their research, they may self-reference from previous work they have written, and in some cases it is becomes obvious who the author is.

To ensure it is totally blind, an author would have to remove all references to themselves and their work in the abstract, which could ruin the research of the paper. Like all the reviewing types, there are benefits and drawbacks to double-blind peer review. The jury is still out on whether it will surpass the most common form (single-blind) in the near future, but it is heading in the right direction.

We have also analysed whether open reviewing is the way forward here,
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What are the limitations of single blind study?

Single blind – In a “Single blind” process, the reviewers’ identities are kept anonymous. Pros: Reviewers, are able to critique a manuscript objectively without any external influence or pressure. At times when there might be more of a need for constructive criticism, a single-blind review safeguards reviewers from the prospect of conflict with the author by maintaining anonymity.

reviewer bias, where there may be some antagonism between reviewer or author academic or professional competition. in a study carried out by the Publishing Research Consortium, only 52% of researchers surveyed would label Single blind reviewing as “effective.” 1

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Does a double-blind trial always involve placebo?

The best and most reliable form of research is the double-blind, placebo-controlled study. A treatment cannot really be said to be proven effective unless it has been examined in properly designed and sufficiently large studies of this type. In these experiments, one group of subjects receives the “real thing”—the active substance being tested.

The other half receives a placebo designed to appear, as much as possible, like the real thing. Individuals in both groups don’t know whether they are getting the real treatment or placebo (they are “blind”). Furthermore, the researchers administering placebo and real treatment are also kept in the dark about which group is receiving which treatment (making it a “double-blind” experiment).

This last part is important, because it prevents the researchers from unintentionally tipping off the study participants, or unconsciously biasing their evaluation of the results. The purpose of this kind of study is to eliminate the power of suggestion.

It is true, although hard to believe, that people given placebo (fake) treatment frequently report dramatic and long-lasting improvements in their symptoms. However, if the people in the real treatment group fare significantly better than those in the placebo group, it is a strong indication that the treatment really works.

What you’ve just read is a highly simplified introduction to a crucial and non-intuitive topic. If you’d like a more in-depth analysis, see the article Why Does This Database Rely on Double-blind Studies?
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Are double-blind experiments reliable?

When drugs or vaccines are being trialed for their effectiveness, there are typically several stages. Double-blind trials are seen as the most reliable type of study because they involve neither the participant nor the doctor knowing who has received what treatment. The aim of this is to minimize the placebo effect and minimize bias. Explain A Situation When A Double-Blind Study Is Not Possible Image Credit: AllaBond/Shutterstock.com
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What bias does double blinding prevent?

Background – The aim of evidence-based medicine is to find the optimal treatment for patients. This process is based on the expertise of the treating practitioner, the characteristics of patients and the best available external evidence, If available, the best external evidence is data from proper conducted randomized controlled trials (RCT), Properly conducted RCT take several measures to minimize bias in order to get valid conclusions, Bias describes a systematic error which leads to deviation of the measured effect away from the true effect of an intervention, The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org. (Accessed 01 Nov 2015)” href=”https://localhost/articles/10.1186/s13643-016-0226-4#ref-CR4″ id=”ref-link-section-d137713439e547″>4 ]. The Cochrane Collaboration defined the following standard domains of bias: random sequence generation, allocation sequence concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective outcome reporting and others. These domains are part of critical appraisal in order to judge validity of trials. Influence of bias on quantitative results can be revealed when conducting sensitivity analyses, The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org. (Accessed 01 Nov 2015)” href=”https://localhost/articles/10.1186/s13643-016-0226-4#ref-CR4″ id=”ref-link-section-d137713439e550″>4 ]. The CONSORT statement (Consolidated Standards of Reporting Trials), a guideline on reporting of outcomes in randomized controlled trials, declared the information to evaluate these domains of bias as mandatory, One measure to reduce bias is blinding. The risk that awareness of the applied intervention bias effects is called 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, The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org. (Accessed 01 Nov 2015)” href=”https://localhost/articles/10.1186/s13643-016-0226-4#ref-CR4″ id=”ref-link-section-d137713439e559″>4 ]. The common term “double-blinded” refers to full avoidance of performance bias by blinding both participants and personnel, Detection bias refers to the risk of how the evaluation of the outcome bias effects. Blinding of outcome assessors reduces detection bias. Outcome assessors (study nurses or investigators) who are aware of the actual treatment may unconsciously or intentionally alter their assessment. Particularly, in case of soft endpoints, e.g. pain blinding of outcome assessors is important. For hard comparators like mortality detection bias is irrelevant, The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org. (Accessed 01 Nov 2015)” href=”https://localhost/articles/10.1186/s13643-016-0226-4#ref-CR4″ id=”ref-link-section-d137713439e565″>4, 7 ]. To express bias quantitatively, the association of lack of blinding and significant results is expressed as an odds ratio. From other medical disciplines, four empirical studies exist on this topic. Each of them compared the results of clinical trials with absent versus present blinding. A meta-analysis of these empirical studies showed an odds ratio of 0.86 (95 % confidence interval 0.74 to 0.99) demonstrating that lack of blinding leads to overestimated treatment effects, Similarly, the degree of detection bias has been investigated. Blinded and unblinded neurologists assessed a medical intervention to treat multiple sclerosis. Although, no treatment benefit was present, the unblinded neurologists’ scores demonstrated an apparent treatment benefit whereas the blinded neurologists’ scores did not, Due to the physical component of interventions, surgical RCT methodology has some specifics. Blinding of the operating surgeon is sometimes impossible. Blinding of patients and outcome assessors is not easily applicable, The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org. (Accessed 01 Nov 2015)” href=”https://localhost/articles/10.1186/s13643-016-0226-4#ref-CR4″ id=”ref-link-section-d137713439e593″>4, 13 ]. For several non-pharmacological treatments, different blinding methods have been investigated, providing detailed methodological information about possible extent of blinding in surgery, However, it remains unclear if ornate blinding measures for surgical interventions are really justified by the gain of better evidence. Cancelling out the blinding measures of patients due to the physical component is very probable and has never been systematically investigated. Until today, influence of detection and performance bias in general and abdominal surgery RCT is unexplored. The objective of the planned systematic review and empirical study is to investigate actual impact on outcomes and future potential of blinding in general and abdominal surgery RCT.
View complete answer

When can an experiment be double-blind?

A type of clinical trial in which neither the participants nor the researcher knows which treatment or intervention participants are receiving until the clinical trial is over. This makes results of the study less likely to be biased.
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When should an experiment be double-blind?

Double blind studies prevent bias when doctors evaluate patients’ outcomes. This improves reliability of clinical trial results. Should you have health complications during a trial, such as a possible drug reaction, your doctor can ‘unblind’ you and find out which treatment you’re receiving.
View complete answer