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Open Access Research

Use of randomisation in clinical trials: a survey of UK practice

Gladys C McPherson1*, Marion K Campbell1 and Diana R Elbourne2

Author Affiliations

1 Health Services Research Unit, University of Aberdeen, 3rd Floor, Foresterhill, Aberdeen, AB25 2ZD, UK

2 Medical Statistics Unit, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK

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Trials 2012, 13:198  doi:10.1186/1745-6215-13-198

Published: 26 October 2012

Abstract

Background

In healthcare research the randomised controlled trial is seen as the gold standard because it ensures selection bias is minimised. However, there is uncertainty as to which is the most preferred method of randomisation in any given setting and to what extent more complex methods are actually being implemented in the field.

Methods

In this paper we describe the results of a survey of UK academics and publicly funded researchers to examine the extent of the use of various methods of randomisation in clinical trials.

Results

Trialists reported using simple randomisation, permuted blocks and stratification more often than more complex methods such as minimisation. Most trialists believed that simple randomisation is suitable for larger trials but there is a high probability of possible imbalance between treatment groups in small trials. It was thought that groups should be balanced at baseline to avoid imbalance and help face-validity. However, very few respondents considered that more complex methods offer any advantages.

Conclusions

This paper demonstrates that for most UK trialists the preferred method of randomisation is using permuted blocks of varying random length within strata. This method eliminates the problem of predictability while maintaining balance across combinations of factors. If the number of prognostic factors is large, then minimisation can be used to provide treatment balance as well as balance over these factors. However, only those factors known to affect outcome should be considered.

Keywords:
Survey; Randomisation; Minimisation