As per ICH-GCP E6, Blinding or Masking is “A procedure in which one or more parties to the trial are kept unaware of the treatment assignment(s). Single-blinding usually refers to the subject(s) being unaware, and double-blinding usually refers to the subject(s), investigator(s), monitor, and, in some cases, data analyst(s) being unaware of the treatment assignment(s).”
Blinding or masking is just a process of test or experiment in which information about the test or test element which leads to bias in final results is hide from the doctor and patient who involved in the particular trial. Bias may be intentional or unconscious. The opposite of Blinding and Masking trial is Open trials in which every one aware about test drug.
Basically blinding is used in those trials or experiments in which two or more drugs are compared without any influence of tester or expectations. Reason behind this is, if you know about the drugs results then in some case you will definitely try to manipulate the process just for positive result but in that situation the actual performance of drug is hide and we got positive results on documents only not in actual status.
Now Blinding is of different type on the basis of trial requirements and protocol documentations.
- Single Blinded trials
- Double Blinded trials
- Triple Blinded trials
Single Blinded Trials
Single Blinded trials are those trials in which patient or subject is unaware about the drugs. Subject don’t know he/she is a “test” subject or included into “experimental control” group. But in this type of trials, subjects are influenced by interaction with the doctors or researchers – this is called experimenter’s bias.
I have picked the best example of single blinded trials from Wikipedia, named as “Pepsi Challenge”. In this trial, marketing person gave two cola labeled cups “A” and “B”. One is filled with Pepsi and Other is filled with Coca Cola. Marketing person know which soda is in which cup but he not informed everything to the subject. Marketing person encourage to try two cups and tell which one you prefer. Now in this case we can see that tester or marketing person can unintentionally give subconscious cues which influence the subjects.
Check below image, it is little funny but real. Single blinded trial doctor know everything, on the other hand patient is unaware about the drugs and trials.
Double Blinded Trials
In Double Blinded Trials neither the participant or subject nor researcher know which participant is categories in which group. The main benefit of these type of trials is to reduce bias between the researcher and the participant. That’s why it is mostly applicable on those trials in which there is some possibilities that the result will be affected by conscious/unconscious bias between on the part of researchers, participant or both. You can see the photographic example in above figure.
Triple Blinded Trials
Same as Double Blinded Trials, Triple Blinded Trials are just extension of Double Blinded Trials in which participant, researcher and person who administrating drug is unaware about the medications or drugs. The committee of the trials is simply given data for groups associated with the trials.
Triple Blinded are theoretically beneficial for the trials committee to evaluate output result according to the main objective of the trials. On the hand it gives a additional layer of security to protect any influences in study results and any bias in trials.