Methodological bias in cluster randomised trials
ABSTRACT Cluster randomised trials can be susceptible to a range of methodological problems. These problems are not commonly recognised by many researchers. In this paper we discuss the issues that can lead to bias in cluster trials.
We used a sample of cluster randomised trials from a recent review and from a systematic review of hip protectors. We compared the mean age of participants between intervention groups in a sample of 'good' cluster trials with a sample of potentially biased trials. We also compared the effect sizes, in a funnel plot, between hip protector trials that used individual randomisation compared with those that used cluster randomisation.
There is a tendency for cluster trials, with evidence methodological biases, to also show an age imbalance between treatment groups. In a funnel plot we show that all cluster trials show a large positive effect of hip protectors whilst individually randomised trials show a range of positive and negative effects, suggesting that cluster trials may be producing a biased estimate of effect.
Methodological biases in the design and execution of cluster randomised trials is frequent. Some of these biases associated with the use of cluster designs can be avoided through careful attention to the design of cluster trials. Firstly, if possible, individual allocation should be used. Secondly, if cluster allocation is required, then ideally participants should be identified before random allocation of the clusters. Third, if prior identification is not possible, then an independent recruiter should be used to recruit participants.
Full-textDOI: · Available from: David Torgerson, Jun 11, 2015
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ABSTRACT: Hip fracture resulting from a fall is one of the main causes of morbidity and functional decay in elderly people. Hip protectors, plastic shields or foam pads fitted in pockets within specially designed underwear could represent an interesting preventive measure available to nursing staff caring for elderly people. The literature from 1993 to July 2005 was reviewed to assess the efficacy and compliance of such devices. In fact, the efficacy of this measure is still controversial because although there is some evidence that in institutions with high rates of hip fracture the use of hip protectors may help to reduce this incidence, there is no evidence of this being true for the majority of older people living at home. Compliance remains poor due to discomfort the practical impairment related to continuous wear of the device. While awaiting further evidence, nursing staff should not use the protectors as a routine measure to prevent hip fracture in institutionalized elderly people and outside a research program. Instead, they should concentrate on the implementation of those preventive measures that have been proved effective.Professioni infermieristiche 59(2):109-18.
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ABSTRACT: This chapter focuses on specific recommendations in the Ottawa Statement pertaining to justification of the cluster randomized trial (CRT) design, the need for research ethics board (REB) review, the identification of research participants, obtaining informed consent, and the role of gatekeepers in knowledge translation (KT) CRTs. Cluster randomization is an ideal study design for evaluating KT interventions, but the choice of cluster randomization must be carefully justified. KT CRTs should be submitted to and approved by a REB. In designing informed consent procedures, researchers should first identify who the research participants are; unless an individual is a research participant, their informed consent is not required. Cluster gatekeepers who have legitimate authority may be approached for permission to enroll a cluster in a KT CRT, but gatekeeper permission is not a substitute for the informed consent of individual research participants.Knowledge Translation in Health Care, 06/2013: pages 378-391; , ISBN: 9781118413548
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ABSTRACT: Cluster randomized trials are trials that randomize clusters of people, rather than individuals. They are becoming increasingly common. A number of innovations have been developed recently, particularly in the calculation of the required size of a cluster trial, the handling of missing data, designs to minimize recruitment bias, the ethics of cluster randomized trials and the stepped wedge design. This article will highlight and illustrate these developments. It will also discuss issues with regards to the reporting of cluster randomized trials.05/2014; 3(3):271-81. DOI:10.2217/cer.14.21