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  • Randomized trial design with spatial constraints_v1.0

    Rights statement: This is a pre-copy-editing, author-produced PDF of an article accepted for publication in International Journal of Epidemiology following peer review. The definitive publisher-authenticated version Robert S McCann, Henk van den Berg, Willem Takken, Amanda G Chetwynd, Emanuele Giorgi, Dianne J Terlouw, Peter J Diggle; Reducing contamination risk in cluster-randomized infectious disease-intervention trials, International Journal of Epidemiology, 47, 1, https://doi.org/10.1093/ije/dyy213 is available online at: https://academic.oup.com/ije/article/47/6/2015/5146518

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Reducing contamination risk in cluster-randomized infectious disease-intervention trials

Research output: Contribution to journalJournal article

E-pub ahead of print
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<mark>Journal publication date</mark>29/10/2018
<mark>Journal</mark>International Journal of Epidemiology
Issue number6
Volume47
Number of pages10
Pages (from-to)2015–2024
Publication statusE-pub ahead of print
Early online date29/10/18
Original languageEnglish

Abstract

Background: Infectious disease interventions are increasingly tested using cluster-randomized trials (CRTs). These trial settings tend to involve a set of sampling units, such as villages, whose geographic arrangement may present a contamination risk in treatment exposure. The most widely used approach for reducing contamination in these settings is the so-called fried-egg design, which excludes the outer portion of all available clusters from the primary trial analysis. However, the fried-egg design ignores potential intra-cluster spatial heterogeneity and makes the outcome measure inherently less precise. Whereas the fried-egg design may be appropriate in specific settings, alternative methods to optimize the design of CRTs in other settings are lacking.

Methods: We present a novel approach for CRT design that either fully includes or fully excludes available clusters in a defined study region, recognizing the potential for intra-cluster spatial heterogeneity. The approach includes an algorithm that allows investigators to identify the maximum number of clusters that could be included for a defined study region and maintain randomness in both the selection of included clusters and the allocation of clusters to either the treatment group or control group. The approach was applied to the design of a CRT testing the effectiveness of malaria vector-control interventions in southern Malawi.

Conclusions: Those planning CRTs to evaluate interventions should consider the approach presented here during trial design. The approach provides a novel framework for reducing the risk of contamination among the CRT randomization units in settings where investigators determine the reduction of contamination risk as a high priority and where intra-cluster spatial heterogeneity is likely. By maintaining randomness in the allocation of clusters to either the treatment group or control group, the approach also permits a randomization-valid test of the primary trial hypothesis.

Bibliographic note

This is a pre-copy-editing, author-produced PDF of an article accepted for publication in International Journal of Epidemiology following peer review. The definitive publisher-authenticated version Robert S McCann, Henk van den Berg, Willem Takken, Amanda G Chetwynd, Emanuele Giorgi, Dianne J Terlouw, Peter J Diggle; Reducing contamination risk in cluster-randomized infectious disease-intervention trials, International Journal of Epidemiology, 47, 1, https://doi.org/10.1093/ije/dyy213 is available online at: https://academic.oup.com/ije/article/47/6/2015/5146518