concealment of allocation

concealment of allocation

The process used to prevent foreknowledge of group assignment in a randomised clinical trial, which differs from blinding. Allocation should be administered by someone who is not responsible for recruiting participants—e.g., the hospital, pharmacy or a central office. Methods of assignment such as date of birth and case record numbers (see quasi-random allocation) are open to manipulation.

Examples, allocation concealment
Centralised randomisation schemes; randomisation schemes controlled by a pharmacy; numbered or coded containers in which capsules from identical-looking, numbered bottles are administered sequentially; on-site computer systems, where allocations are in a locked unreadable file; sequentially-numbered, opaque sealed envelopes.
References in periodicals archive ?
Concealment of allocation occurred, but method of randomization and intention-to-treat analysis were not reported.
Major strengths were randomized design with concealment of allocation, very good power, masking, objective measurement of blood loss, and attempts to standardize treatment other than the interventions.
In 24 of 39 trials concealment of allocation assignment to treatment group was unclear and in one trial it was clearly inadequate.
STUDY DESIGN AND VALIDITY Patients were randomized using adequate concealment of allocation, in an unblinded manner, to receive a hip protector or to not receive one.
The second limitation found in these trials is the one that causes the most concern: the inadequate concealment of allocation assignment.