Why transition from alternation to randomisation in clinical trials was made

BMJ 1999;319:1372 ( 20 November )

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Why transition from alternation to randomisation in clinical trials was made

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EDITOR $---$ It is time to put the record straight about ways of controlling selection bias when generating comparison groups inclinical trials. D'Arcy Hart has done history a great serviceby noting that Bradford Hill's motivation for replacing alternationwith randomisation was "to better conceal the allocation schedule."¹This is what Guy Scadding (who, with D'Arcy Hart, is the othersurviving member of the team who designed the streptomycin trial)told Mike Clarke and me when we visited him on 10 June 1999, andwhat Bradford Hill told William Silverman and me when we visitedhim on 3 April1982.

Bradford Hill's motivation for concentrating on the concealment of the allocation schedule in the streptomycin trial seemslikely to have been stimulated more than a decade earlier. A MedicalResearch Council trial of serum treatment for lobar pneumoniahad used an (unconcealed) allocation schedule based on alternation,²and important imbalances in the . . . [Full text of this article]

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