Blinding Flashcards
What may happen if a clinician finds out the group allocation of the patients he is treating in a trial?
May over-react to side effects in those who receive active medication
May downplay side effects in those receiving placebo
What may happen if patient finds out the group they are allocated to?
May report less improvement if in placebo
May report more improvement if in active group
What may happen if assessor finds out group allocation?
May tend to overrate positive sx in active group and underrate ill effects in placebo group
Types of blinding
Open label Single Double Triple Unblinding
What is open label?
All parties aware of treatment being received after randomisation
What is single blind?
Either patient or clinician remains unaware of treatment assignment
What is double blind?
Both patient and investigator are unaware of allocated group
What is tribpe blind?
Patient, investigator and those who adjudicate study outcomes (assessor) unaware of group allocation
What is unblinding?
Disclosure (planned on unintended) of allocation of one, group of all of the participants
At what stages does allocation concealment occur?
Generation of random list
Assignment of participants to groups
What is allocation concealment?
Keeping random sequence secret from investigator, clinician and patient
What may happen if the clinician becomes aware of the randomisation sequence during assignment?
They may allocate patients to a specific group depending on whether they feel the patient will do well or poorly
What may happen is patients become aware of the randomisation sequence during assignment?
Patient may wait until they will get put into intervention they want
How is allocation concealment done?
Person who generates allocation sequence should not be same person who recruits/assigns subjects
Use centralised or remote randomisation service
If same personnel involved in generating sequence and allocation, use SNOSE
What is SNOSE?
Serially Numbered, Opaque, Sealed Envelopes containing random sequence
