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R: st: multile comparison among incidence rates


From   "Carlo Lazzaro" <carlo.lazzaro@tin.it>
To   <statalist@hsphsun2.harvard.edu>
Subject   R: st: multile comparison among incidence rates
Date   Thu, 3 Apr 2008 18:56:08 +0200

Dear Svend,
thanks a lot for your kind reply and for the example.

I beg your pardon for having been not clear enough.

Actually, I would like to compare the significant difference of all the
incidence rates. 

Let'say:

Patients enrolled to receive drug A reported 200 relapses during a 6-month
follow-up;
Patients enrolled to receive drug B reported 150 relapses during a 6-month
follow-up;
Patients enrolled to receive drug C reported 220 relapses during a 6-month
follow-up.

I have in mind something like multiple comparisons with Bonferroni's
correction via ANOVA with continuous variables, but I do not know whether a
similar procedure does exist in the dichotomous variables setting (I have
unsuccessfully scanned some epidemiology textbook searching for this issue,
but I was not able to find nothing more than chi2 and two-sample
comparisons).


Thanks a lot agin and Kind Regards,

Carlo
-----Messaggio originale-----
Da: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di Svend Juul
Inviato: giovedý 3 aprile 2008 17.56
A: statalist@hsphsun2.harvard.edu
Oggetto: Re: st: multile comparison among incidence rates 

Carlo wrote:
 
I would like to compare three incidence rates (the only effectiveness end
point available) concerning three group of patients with the same disease,
treated with three different drugs and followed-up for six months.
 
Is there any way to do it in Stata/SE 9.2? Is there any reference about your
hints?
 
=========================================================
 
Carlo,
 
It is not quite clear to me what you mean by "compare three incidence
rates". Is it a question of significant difference or estimation of
incidence rate ratios or rate differences? And do you want to compare
B vs A and C vs A only, or do you also want to compare B vs C?
 
Below I used -ci- to estimate the individual incidence rates and
-poisson- to estimate incidence rate ratios (imagine that -agecat-
represents the drugs to be compared).
 
    webuse dollhill3.dta
    by agecat, sort: ci deaths, poisson exposure(pyears)
    xi: poisson deaths i.agecat, exposure(pyears) irr
 
Hope this helps
Svend

________________________________________________________ 
 
Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6 
DK-8000 Aarhus C,  Denmark 
Phone, work:   +45 8942 6090 
Phone, home:   +45 8693 7796 
Fax:           +45 8613 1580 
E-mail:        sj@soci.au.dk 
_________________________________________________________ 

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