Allocation concealment and blinding: when ignorance is bliss

Peta M Forder, Val J Gebski and Anthony C Keech
Med J Aust 2005; 182 (2): . || doi: 10.5694/j.1326-5377.2005.tb06584.x
Published online: 17 January 2005

Good study design involves minimising all possible sources of bias. Two important sources of bias arise through failure to mask (ie, conceal), first, the randomisation process and, second, the treatments after randomisation. Allocation concealment is the term used to describe the procedure for protecting the randomisation process so that the treatment to be allocated is not known before the patient is entered into the study. Blinding relates to the masking of the treatments after randomisation — from the patient, the investigator or the outcomes assessor. Without exception, allocation concealment is achievable in all randomised clinical trials. In contrast, it is not always possible to blind people to study treatments received. The CONSORT statement strongly encourages detailed reporting of the allocation concealment process and the measures taken to preserve blinding (Box 1).1

  • Peta M Forder1
  • Val J Gebski2
  • Anthony C Keech3

  • NHMRC Clinical Trials Centre, University of Sydney, Sydney, NSW.



We thank Rhana Pike, Editor in the Life Sciences (ELS), for expert assistance in preparing this manuscript.

Competing interests:

None identified.


remove_circle_outline Delete Author
add_circle_outline Add Author

Do you have any competing interests to declare? *

I/we agree to assign copyright to the Medical Journal of Australia and agree to the Conditions of publication *
I/we agree to the Terms of use of the Medical Journal of Australia *
Email me when people comment on this article

Online responses are no longer available. Please refer to our instructions for authors page for more information.