Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors

At the outset, I would like to congratulate CMAJ and authors for wonderful research paper on evidence regarding Blinding and bias. I feel there is undue importance given to blinding in RCTs. Though it is very important for results to be unbiased by blinding technique, it can not bypass objectivity of measurements whenever possible. Except subjective phenomenon like perception after taking intervention, some of the psychological parameters and interventions where blinding is not possible due to ethical reasons like surgery vs medical management, all RCTs should measure objective parameter if possible. It may be difficult to combine in the meta-analysis such studies where blinding not possible with other types of where objective parameter may be appropriate.

Dr.Pankaj B Shah, Professor,Dept.of Community Medicine, SRMC & RI,SRU, Chennai-India

Conflict of Interest:

None declared