Allocation concealment

Successful randomisation is inversely related to the chance of a trial finding a treatment effect (in one review, 58% of randomised studies, where allocation could have been compromised, found a benefit of the new treatment versus 9% of randomised trials with adequate allocation concealment). 

Note that allocation concealment in randomisation is different to blinding (see Table... 

Comparative studies Artemisinin derivatives have been compared with quinine in cerebral malaria in African children nine randomized clinical trials were included in the analysis [9M] pjyg trials had adequate allocation concealment. Seven compared artemether with quinine ( =1220) and two compared arteether with quinine ( = 194). There were no significant differences between artemisinin derivatives and quinine in preventing mortality (RR=0.91 95% CI=0.73,1.1). The only serious adverse event was fatal black water disease in a patient who took quinine. 

J. Pildal, A. Hrobjartsson, K. J. Jorgensen, J. Hilden, D. G. Altman, and P. C. Gotzsche. Impact of allocation concealment on conclusions drawn from meta-analyses of randomized trials, Internal Journal of Epidemiology, 36, 4, 847-857, 2007. 

Although many examples of clinical investigation can be found throughout the history of medicine, the RCT emerged in the mid-20th century as the most powerful and scientifically sound way to establish the efficacy and safety of medicines. In 1948, Austin Bradford Hill used the statistical method of randomization with concealment of the allocation code to reduce biases related to selection and analysis of patients... 

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