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From |
Jonathan Sterne <Jonathan.Sterne@bristol.ac.uk> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Questions on a meta-regression problem |

Date |
Fri, 24 Apr 2009 08:32:56 +0100 |

Best wishes Jonathan Sterne

Date: Thu, 23 Apr 2009 21:38:22 +0100 From: "G Livesey" <glivesey@inlogic.co.uk> Subject: st: Questions on a meta-regression problem Dear Statalisters I am meta-analysing prospective studies relating health outcomes to nutrient dose, and would gladly welcome comments and help with solutions where possible. Rather than meta-analyse the slopes from each study to obtain a mean, tau and se for the slopes (such as with the GLST module) , I would like the primary unit of study to be the quantile (irater than the study level) and use dose values (as continuous) rather than quantile levels for dose (categories). To achieve this involves some prior calculations to bring a common metric to the dose and a common referent dose, which otherwise differ between studies. The broader range of nutrient dose than found in individual studies (>2 fold) would help with fitting an overall slope and viewing the wider picture. Such advantage seems not to be without other, possible disadvantage - unless statlisters have a solution: The problem is that quantiles within studies may not be truly independent (e.g. Studies might not have identical conditions or may be biased). The question is. therefore, is there (or can there be) a solution to this problem? No ready made solution is obvious (to me) in a search of meta-analysis commands or net searches. If not, what post-analyses might be done to limit any error incurred? For example, metareg P-values for the coefficients might be recalculated to a lower number of degrees of freedom, likewise for tau, but how should one define the degrees of freedom for the coefficients and for tau, and how should one perform an appropriate recalculation of Tau (the estimate of Tau within studies is close to zero, possibly averaging near zero, though may not always be so)? The problem does not seems extensive with this dataset, however, I would appreciate viewpoints or potential solutions on this issue . An example dataset with meta-regression commands is described below. But does anyone know of another module that could offer a better approach to this problem. With thanks, and in admiration of the many solutions statalisters release each day on the statalist. Geoff. Livesey.

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