Cochran-Mantel-Haenszel?

[Charlotte-9]

Dear all,

I would like to check for an association between the uptake of breast
screening and bowel screening whilst controlling for a third variable,
ethnicity.  Is the Cochran-Mantel-Haenszel test the appropriate procedure
to use here?  I have dependencies in the data since I am comparing the
same groups of people (e.g.  I have the proportion of people in an ethnic
group who undertook breast screening and the proportion of people from
that same group who undertook bowel screening).

Thanks for any help you can offer,

Lou

[Albert-Jan Roskam]

Hi Lou,

Have a look at the following FREE article:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14567763&dopt=Citation
or if that link is not displayed properly:
http://tinyurl.com/29fafh

*** ABSTRACT ***
Alternatives for logistic regression in
cross-sectional studies: an empirical comparison of
models that directly estimate the prevalence ratio.
Barros AJ, Hirakata VN.

Programa de Pos-graduacao em Epidemiologia,
Universidade Federal de Pelotas, Brazil.
[hidden email]

BACKGROUND: Cross-sectional studies with binary
outcomes analyzed by logistic regression are frequent
in the epidemiological literature. However, the odds
ratio can importantly overestimate the prevalence
ratio, the measure of choice in these studies. Also,
controlling for confounding is not equivalent for the
two measures. In this paper we explore alternatives
for modeling data of such studies with techniques that
directly estimate the prevalence ratio. METHODS: We
compared Cox regression with constant time at risk,
Poisson regression and log-binomial regression against
the standard Mantel-Haenszel estimators. Models with
robust variance estimators in Cox and Poisson
regressions and variance corrected by the scale
parameter in Poisson regression were also evaluated.
RESULTS: Three outcomes, from a cross-sectional study
carried out in Pelotas, Brazil, with different levels
of prevalence were explored: weight-for-age deficit
(4%), asthma (31%) and mother in a paid job (52%).
Unadjusted Cox/Poisson regression and Poisson
regression with scale parameter adjusted by deviance
performed worst in terms of interval estimates.
Poisson regression with scale parameter adjusted by
chi2 showed variable performance depending on the
outcome prevalence. Cox/Poisson regression with robust
variance, and log-binomial regression performed
equally well when the model was correctly specified.
CONCLUSIONS: Cox or Poisson regression with robust
variance and log-binomial regression provide correct
estimates and are a better alternative for the
analysis of cross-sectional studies with binary
outcomes than logistic regression, since the
prevalence ratio is more interpretable and easier to
communicate to non-specialists than the odds ratio.
However, precautions are needed to avoid estimation
problems in specific situations.

Cheers!!
Albert-Jan

--- Lou <[hidden email]> wrote:

> Dear all,
>
> I would like to check for an association between the
> uptake of breast
> screening and bowel screening whilst controlling for
> a third variable,
> ethnicity.  Is the Cochran-Mantel-Haenszel test the
> appropriate procedure
> to use here?  I have dependencies in the data since
> I am comparing the
> same groups of people (e.g.  I have the proportion
> of people in an ethnic
> group who undertook breast screening and the
> proportion of people from
> that same group who undertook bowel screening).
>
> Thanks for any help you can offer,
>
> Lou
>

Cheers!
Albert-Jan

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Did you know that 87.166253% of all statistics claim a precision of results that is not justified by the method employed? [HELMUT RICHTER]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



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