Allocation Concealment in Randomised Trials

Schulz, K. F., & Grimes, D. A. (2002). Allocation Concealment in Randomised Trials: Defending Against Deciphering. The Lancet, 359(9306), 614-618.

Type

Journal article

Intellectual base

Primary research

Year

2002

Volume

359

Issue

9306

Pages

614-618

ISSN

0140-6736

DOI

10.1016/s0140-6736(02)07750-4

DOI registrant

Elsevier

Link

https://doi.org/10.1016/S0140-6736(02)07750-4

Cited by

2 citations across 2 artifacts.

Each citation links to the sentence it supports in the citing article.

Mechanisms

• Central Randomization and Masking Service
  • Its strength is enforcing allocation concealment — preventing anyone from foreseeing or steering the next assignment — while delivering uniform masking across every site from one place.

    This sourceDefines allocation concealment as preventing foreknowledge or steering of upcoming treatment assignments.

• Permuted-Block Sequence
  • It misleads when the block size is fixed and known and allocation is not concealed: implementers can anticipate upcoming assignments and steer who enrolls when, producing selection bias — the classic hazard that motivates allocation concealment in the first place.

    This sourceExplains how fixed, known block sizes without allocation concealment make assignments predictable and permit enrollment manipulation that creates selection bias.

Verification

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