rials 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 ie which treatment was received in order to avoid bias ID: 815443
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Slide1
Blinding in
c
linical
t
rials
Slide2Blinding is a procedure in which one or more parties in a trial are kept
unaware of which treatment arms participants have been assigned to, i.e. which treatment was received in order to avoid bias.Blinding is an important aspect of any trial. How a trial was blinded should be accurately recorded in order to allow readers to interpret the results of a study. If blinding is broken during a trial on individual patients, it needs to be statistically and/or ethically explained at the end.
Blinding of the trial
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Slide3Blinding is used to prevent conscious or unconscious
bias in the design of a clinical trial and how it is carried out. This is important because bias can affect recruitment and allocation, care, attitudes, assessments, etc.It is used to ensure the objectivity of trial results
Why do we blind?
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Slide4Sources of bias include:
Patient being treatedClinical staff administering treatmentDoctor assessing treatmentTeam interpreting trial resultsWhat are the potential sources of bias in a trial?
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Slide5Participants in a trial
Clinicians and data collectors Outcome adjudicators and data analystsWho can be blinded in clinical trials?5
Slide6Types of blinding
TypeDescriptionUnblinded or open labelAll are aware of the treatment the participant receivesSingle blind or single-maskedOnly the participant is unaware of the treatment they receive
Double blind or double-maskedThe participant and the clinicians / data collectors are unaware of the treatment the participant receives
Triple blind
Participant, clinicians / data collectors and outcome adjudicators / data analysts are all unaware of the treatment the participant receives.
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Slide7A trial in which no blinding is used and all parties are aware of the treatment groups. Also called
open label.Should be used:For surgical procedures*When changes in lifestyle are requiredWhen endpoints are objective
and cannot be interpreted in different ways
For case studies with life-threatening situations
In
post-marketing surveillance
When ethical considerations do
not permit
blinding
When no control group can be
used
Unblinded
trial
*It should be noted that surgical procedures can be blinded but are extremely difficult to blind. This is very hard especially if participants can be compared.
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Slide8A trial in which one party, either the investigator or participant, is unaware of which treatment the participant is taking. Also called
single-masked trial.Provides some control when double blinding is impossibleUsed when the experimental medicine and control cannot be manufactured identicallySingle-blind trial
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Slide9A clinical trial design in which neither the participants nor the study staff know which participants are receiving the experimental medicine, and which are receiving a placebo (or another therapy).
Double-blind trials are thought to produce objective results, since the expectations of the doctor and the participant do not affect the outcome. Also called double-masked trial.Best-controlled trial designDecreased chance of observational biasShould be used whenever possibleDouble-blind trial9
Slide10A triple blind trial means that patients, clinicians, data collectors, outcome adjudicators and data analysts are denied access to details of group assignment. This ensures that bias for or against the tested treatment is very unlikely to occur.
Medicine may still be labelled as A or B during analysisThe analyst is blinded as to which treatment is whichHelps to avoid bias in the analysis of results.Triple blind10
Slide11Unblinding
is the disclosure of the treatment to a participant or study team. It protects the participants in case of medical or safety reasons.In a crossover design, the participant may only be unblinded for the most recent dose.
The protocol for unblinding should be described upfront, and must include information about when and by whom is to be done
.
Unblinding the trial
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Slide12Karanicolas
, P., Farrokhyar, F., & Bhandari, M. (2010). Blinding: Who, what, when, why, how? Canadian Journal of Surgery, 53(5), 345–348. Retrieved 21 August, 2015, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2947122/ Schulz, K.F., Grimes, D.A. (2002) Blinding in randomised trials: hiding who got what. Lancet, 359, 696-700. Retrieved 21 August, 2015,
fromhttp
://apps.who.int/rhl/LANCET_696-700.pdf
References
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