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Publication - Dr Kyla Thomas

    How to compare instrumental variable and conventional regression analyses using negative controls and bias plots

    Citation

    Davies, N, Thomas, K, Taylor, A, Taylor, G, Martin, R, Munafo, M & Windmeijer, F, 2017, ‘How to compare instrumental variable and conventional regression analyses using negative controls and bias plots’. International Journal of Epidemiology, vol 46., pp. 2067-2077

    Abstract

    There is increasing interest in the use of instrumental variable analysis to overcome unmeasured confounding in observational pharmacoepidemiological studies. This is partly because instrumental variable analyses are potentially less biased than conventional regression analyses. However, instrumental variable analyses are less precise, and regulators and clinicians find it difficult to interpret conflicting evidence from instrumental variable compared with conventional regression analyses. In this paper, we describe three techniques to assess which approach (instrumental variable versus conventional regression analyses) is least biased: negative control outcomes; negative control populations; and tests of covariate balance. We illustrate these methods using an analysis of the effects of smoking cessation therapies (varenicline) prescribed in primary care.

    Full details in the University publications repository