Re: [R] meta-analysis, outcome = OR associated with a continuous independent variable
I do not see any major difficulties with this case either. Suppose you have OR = 1.5 (with 95% CI: 1.19 to 1.90) indicating that the odds of a particular outcome (e.g., disease) is 1.5 times greater when the (continuous) exposure variable increases by one unit. Then you can back-calculate the SE of log(OR) = .41 with sei = (ln(ci.ub) - ln(ci.lb)) / (2*1.96), which in this case is approximately 0.12. The sampling variance of log(OR) is then vi = sei^2. Now you have everything for the meta-analysis, using any of the packages mentioned. What Thomas already mentioned is that the 'one unit increase' must mean the same thing in each study. Therefore, if the exposure variable is measured in months in one study and in years in another study, then the odds ratios are obviously not directly comparable. If the units are just multiples of each other, then you can easily calculate what the OR would be when putting the exposure variable on the same scale. For example, an OR of 1.5 for a one month increase in exposure is the same as an OR of 1.5^12 = 129.75 for a one year increase in exposure. Best, Wolfgang -- Wolfgang Viechtbauer, Ph.D., Statistician Department of Psychiatry and Psychology School for Mental Health and Neuroscience Faculty of Health, Medicine, and Life Sciences Maastricht University, P.O. Box 616 (VIJV1) 6200 MD Maastricht, The Netherlands +31 (43) 388-4170 | http://www.wvbauer.com -Original Message- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Thomas Lumley Sent: Wednesday, April 04, 2012 23:42 To: Marie-Pierre Sylvestre Cc: r-help@r-project.org Subject: Re: [R] meta-analysis, outcome = OR associated with a continuous independent variable On Thu, Apr 5, 2012 at 8:24 AM, Marie-Pierre Sylvestre mp.sylves...@gmail.com wrote: Hello everyone, I want to do a meta-analysis of case-control studies on which an OR was computed based on a continuous exposure. I have found several several packages (metafor, rmeta, meta) but unless I misunderstood their main functions, it seems to me that they focus on two-group comparisons (binary independent variable), and do not have the option of using a continuous independent variable. There's no problem in using continuous exposures in meta.summaries() in the rmeta package. For each study, compute your log odds ratio and its standard error, and feed them in. You just need to make sure that the odds ratio is in the same units in each study, of course. -thomas -- Thomas Lumley Professor of Biostatistics University of Auckland __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting- guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] meta-analysis, outcome = OR associated with a continuous independent variable
LIKE:) On 2012-4-5 15:03, Viechtbauer Wolfgang (STAT) wrote: I do not see any major difficulties with this case either. Suppose you have OR = 1.5 (with 95% CI: 1.19 to 1.90) indicating that the odds of a particular outcome (e.g., disease) is 1.5 times greater when the (continuous) exposure variable increases by one unit. Then you can back-calculate the SE of log(OR) = .41 with sei = (ln(ci.ub) - ln(ci.lb)) / (2*1.96), which in this case is approximately 0.12. The sampling variance of log(OR) is then vi = sei^2. Now you have everything for the meta-analysis, using any of the packages mentioned. What Thomas already mentioned is that the 'one unit increase' must mean the same thing in each study. Therefore, if the exposure variable is measured in months in one study and in years in another study, then the odds ratios are obviously not directly comparable. If the units are just multiples of each other, then you can easily calculate what the OR would be when putting the exposure variable on the same scale. For example, an OR of 1.5 for a one month increase in exposure is the same as an OR of 1.5^12 = 129.75 for a one year increase in exposure. Best, Wolfgang -- Wolfgang Viechtbauer, Ph.D., Statistician Department of Psychiatry and Psychology School for Mental Health and Neuroscience Faculty of Health, Medicine, and Life Sciences Maastricht University, P.O. Box 616 (VIJV1) 6200 MD Maastricht, The Netherlands +31 (43) 388-4170 | http://www.wvbauer.com -Original Message- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Thomas Lumley Sent: Wednesday, April 04, 2012 23:42 To: Marie-Pierre Sylvestre Cc: r-help@r-project.org Subject: Re: [R] meta-analysis, outcome = OR associated with a continuous independent variable On Thu, Apr 5, 2012 at 8:24 AM, Marie-Pierre Sylvestre mp.sylves...@gmail.com wrote: Hello everyone, I want to do a meta-analysis of case-control studies on which an OR was computed based on a continuous exposure. I have found several several packages (metafor, rmeta, meta) but unless I misunderstood their main functions, it seems to me that they focus on two-group comparisons (binary independent variable), and do not have the option of using a continuous independent variable. There's no problem in using continuous exposures in meta.summaries() in the rmeta package. For each study, compute your log odds ratio and its standard error, and feed them in. You just need to make sure that the odds ratio is in the same units in each study, of course. -thomas -- Thomas Lumley Professor of Biostatistics University of Auckland __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting- guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] meta-analysis, outcome = OR associated with a continuous independent variable
For some reason I was under the false impression that these packages were made for meta-analyses of RCT-like studies in which two groups are compared. I am glad to see that I was wrong and that I can use one of these packages. All studies reported using the same units for the exposure so the OR are comparable. Thanks for your responses, MP Le , Viechtbauer Wolfgang (STAT) wolfgang.viechtba...@maastrichtuniversity.nl a écrit : I do not see any major difficulties with this case either. Suppose you have OR = 1.5 (with 95% CI: 1.19 to 1.90) indicating that the odds of a particular outcome (eg, disease) is 1.5 times greater when the (continuous) exposure variable increases by one unit. Then you can back-calculate the SE of log(OR) = .41 with sei = (ln(ci.ub) - ln(ci.lb)) / (2*1.96), which in this case is approximately 0.12. The sampling variance of log(OR) is then vi = sei^2. Now you have everything for the meta-analysis, using any of the packages mentioned. What Thomas already mentioned is that the 'one unit increase' must mean the same thing in each study. Therefore, if the exposure variable is measured in months in one study and in years in another study, then the odds ratios are obviously not directly comparable. If the units are just multiples of each other, then you can easily calculate what the OR would be when putting the exposure variable on the same scale. For example, an OR of 1.5 for a one month increase in exposure is the same as an OR of 1.5^12 = 129.75 for a one year increase in exposure. Best, Wolfgang -- Wolfgang Viechtbauer, Ph.D., Statistician Department of Psychiatry and Psychology School for Mental Health and Neuroscience Faculty of Health, Medicine, and Life Sciences Maastricht University, PO Box 616 (VIJV1) 6200 MD Maastricht, The Netherlands +31 (43) 388-4170 | http://www.wvbauer.com -Original Message- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Thomas Lumley Sent: Wednesday, April 04, 2012 23:42 To: Marie-Pierre Sylvestre Cc: r-help@r-project.org Subject: Re: [R] meta-analysis, outcome = OR associated with a continuous independent variable On Thu, Apr 5, 2012 at 8:24 AM, Marie-Pierre Sylvestre mp.sylves...@gmail.com wrote: Hello everyone, I want to do a meta-analysis of case-control studies on which an OR was computed based on a continuous exposure. I have found several several packages (metafor, rmeta, meta) but unless I misunderstood their main functions, it seems to me that they focus on two-group comparisons (binary independent variable), and do not have the option of using a continuous independent variable. There's no problem in using continuous exposures in meta.summaries() in the rmeta package. For each study, compute your log odds ratio and its standard error, and feed them in. You just need to make sure that the odds ratio is in the same units in each study, of course. -thomas -- Thomas Lumley Professor of Biostatistics University of Auckland __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting- guide.html and provide commented, minimal, self-contained, reproducible code. [[alternative HTML version deleted]] __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] meta-analysis, outcome = OR associated with a continuous independent variable
You can get an OR from a 2x2 table (which is equivalent to doing logistic regression with a single dummy variable that indicates the group) or from some continuous exposure (where the logistic regression model will then include that continuous variable). The various packages are set up to accept counts for 2x2 tables and then will compute the OR (or rather, log(OR)) for you. If you have ORs from the second case, you simply calculate the log(ORs) yourself and supply them to the appropriate function from the packages. Best, Wolfgang -Original Message- From: mp.sylves...@gmail.com [mailto:mp.sylves...@gmail.com] Sent: Thursday, April 05, 2012 15:23 To: Viechtbauer Wolfgang (STAT); Marie-Pierre Sylvestre Cc: r-help@r-project.org; Thomas Lumley Subject: Re: RE: [R] meta-analysis, outcome = OR associated with a continuous independent variable For some reason I was under the false impression that these packages were made for meta-analyses of RCT-like studies in which two groups are compared. I am glad to see that I was wrong and that I can use one of these packages. All studies reported using the same units for the exposure so the OR are comparable. Thanks for your responses, MP __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
[R] meta-analysis, outcome = OR associated with a continuous independent variable
Hello everyone, I want to do a meta-analysis of case-control studies on which an OR was computed based on a continuous exposure. I have found several several packages (metafor, rmeta, meta) but unless I misunderstood their main functions, it seems to me that they focus on two-group comparisons (binary independent variable), and do not have the option of using a continuous independent variable. If this is right, do you have any suggestions for a meta-analysis with continuous independent variable? I using lme or lme4 with weights my only option? Thanks in advance, MP [[alternative HTML version deleted]] __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] meta-analysis, outcome = OR associated with a continuous independent variable
On Thu, Apr 5, 2012 at 8:24 AM, Marie-Pierre Sylvestre mp.sylves...@gmail.com wrote: Hello everyone, I want to do a meta-analysis of case-control studies on which an OR was computed based on a continuous exposure. I have found several several packages (metafor, rmeta, meta) but unless I misunderstood their main functions, it seems to me that they focus on two-group comparisons (binary independent variable), and do not have the option of using a continuous independent variable. There's no problem in using continuous exposures in meta.summaries() in the rmeta package. For each study, compute your log odds ratio and its standard error, and feed them in. You just need to make sure that the odds ratio is in the same units in each study, of course. -thomas -- Thomas Lumley Professor of Biostatistics University of Auckland __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
