[R] R: Comparing summary hazard ratios in meta-analysis

[Mario Petretta]

Many many thanks to Michael Dewey and to Viechtbauer Wolfgang for the kindly and useful replay !!

I only ask to Wolfgang if I should log-transform hazard ratios and compute standard error only for the summary hazard ratio estimates or, as suggested by Michael, for each single study, combining them in a single data frame and thereafter performing the meta-regression incorporating the moderator.

Mario

-----Messaggio originale-----
Da: Viechtbauer Wolfgang (STAT) [mailto:wolfgang.viechtbauer a maastrichtuniversity.nl] 
Inviato: venerdì 21 novembre 2014 15:37
A: Michael Dewey; Mario Petretta; r-help a r-project.org
Oggetto: RE: [R] Comparing summary hazard ratios in meta-analysis

Those hazard ratios and CIs seem a bit strange. On the log-scale, they should be symmetric, but they are not. Could be due to heavy rounding though. At any rate, it comes down to this:

hr    <- c(3.12, 1.15)
ci.lb <- c(2.2, 1.03)
ci.ub <- c(4.1, 2.6)
meta  <- c(1,2)

### log-transform hazard ratios and compute standard error based on the CI bounds yi  <- log(hr) sei <- (log(ci.ub) - log(ci.lb)) / (2*1.96)

library(metafor)
res <- rma(yi ~ factor(meta), sei=sei, method="FE") res

So, yes, the two hazard ratios are significantly different from each other.

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-bounces a r-project.org 
> [mailto:r-help-bounces a r-project.org]
> On Behalf Of Michael Dewey
> Sent: Friday, November 21, 2014 13:25
> To: Mario Petretta; r-help a r-project.org
> Subject: Re: [R] Comparing summary hazard ratios in meta-analysis
> 
> On 21/11/2014 08:51, Mario Petretta wrote:
> > Dear all,
> >
> > I use R 3.1.1 for Windows.
> >
> > I performed two different meta-analysis assessing the prognostic 
> > value
> of
> > two different tests in patients with coronary artery disease. The 
> > study included in the two analysis are different.
> 
> That makes life simpler.
> 
> >
> > The variable of interest in dichotomous (normal/abnormal result) for
> both
> > tests.
> >
> > The effects size is hazard ratio and its standard error (ln units) 
> > for
> both
> > meta-analysis.
> 
> It sounds as though you might want to use meta-regression. You will 
> need a single data frame containing at least log hr, se of log hr, an 
> identifier for the test. I would use the metafor package for this, 
> look in the documentation for how to incorporate a moderator (your 
> test variable). The advantage of meta-regression is that you not only 
> get a test but also a measure of how different the hr are with a 
> confidence interval.
> 
> > I would like to statistically compare the two summary hazard ratios 
> > and
> 95%
> > CI (eform) obtained from the two meta-analysis.
> >
> > For one meta-analysis: HR 3.12 (95% CI 2.2 - 4.1) For the other: HR 
> > 1.25 (95% CI 1.03 - 2.6)
> >
> > It is possible or I'm comparing apples with oranges?
> >
> > Any suggestion is welcome.
> >
> > -------------------------------------------------------
> > Mario Petretta
> > Associate Professor of Internal Medicine Department of Translational 
> > Medical Sciences Naples University Federico II Italy


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