Blinding and Allocation Concealment

OVERVIEW

Blinding and allocation concealment are used in Randomised control trials (RCTs) to reduce systematic bias

BLINDING

Blinding is the process by which trial participants and their relatives, care-givers, data collectors and/or those adjudicating outcomes are unaware of which treatment is being given to the individual participants

Benefits

  • Prevents clinicians from consciously or subconsciously treating patients differently based on treatment allocation (e.g. detection bias)
  • Prevents data collectors from introducing bias when there is a subjective assessment to be made for eg “pain score” (e.g. observer bias)
  • Prevents outcome assessors from introducing bias when there is a subjective outcome assessment to be made (e.g. Glasgow outcome Score) (e.g. observer bias)
  • Prevents patients from introducing bias when followed up (recall bias)

Description of blinding

  • The 2010 CONSORT Statement specifies that authors and editors should not use the terms “single-blind,” “double-blind,” and “triple-blind” as the terms are ambiguous
  • instead reports of blinded RCT should discuss “If done, who was blinded after assignment to interventions (for example, participants, care providers, those assessing outcomes) and how

ALLOCATION CONCEALMENT

Allocation concealment is performed when the treatment allocation system is set up so that the person enrolling participants does not know in advance which treatment the next person will get

  • it is necessary for randomisation to be successful in an RCT
  • Proper allocation concealment shields knowledge of forthcoming assignments, whereas proper random sequence generation prevents correct anticipation of future assignments based on knowledge of past assignments 
  • Methods used for allocation concealment include sealed envelope technique, telephone or web based randomization.

BLINDING VERSUS ALLOCATION CONCEALMENT

  • Allocation concealment ensures that the treatment to be allocated is not known before the patient is entered into the study
  • Blinding ensures that the patient / physician is blinded to the treatment allocation after enrollment into the study

References and Links

LITFL

FOAM and web resources


CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the  Clinician Educator Incubator programme, and a CICM First Part Examiner.

He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.

His one great achievement is being the father of three amazing children.

On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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