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A note on calculating asymptotic confidence intervals for the adjusted risk difference and number needed to treat in the Cox regression model |
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| Authors: | Ruediger P Laubender Ralf Bender |
| Institution: | 1. German Cancer Consortium (DKTK), , Heidelberg, Germany;2. Institute of Medical Informatics, Biometry, and Epidemiology (IBE), Faculty of Medicine, Ludwig–Maximilians–University Munich, , Munich, Germany;3. German Cancer Research Center (DKFZ), , Heidelberg, Germany;4. Department of Medical Biometry, Institute for Quality and Efficiency in Health Care (IQWiG), , Cologne, Germany;5. Faculty of Medicine, University of Cologne, , Cologne, Germany |
| Abstract: | Recently, Laubender and Bender (Stat. Med. 2010; 29: 851–859) applied the average risk difference (RD) approach to estimate adjusted RD and corresponding number needed to treat measures in the Cox proportional hazards model. We calculated standard errors and confidence intervals by using bootstrap techniques. In this paper, we develop asymptotic variance estimates of the adjusted RD measures and corresponding asymptotic confidence intervals within the counting process theory and evaluated them in a simulation study. We illustrate the use of the asymptotic confidence intervals by means of data of the Düsseldorf Obesity Mortality Study. Copyright © 2013 John Wiley & Sons, Ltd. |
| Keywords: | adjustment confidence intervals confounding counting process Cox proportional hazards regression exposure impact number (EIN) number needed to be exposed (NNE) number needed to treat (NNT) risk difference (RD) |