From Ricardo Ovaldia <[email protected]> To [email protected] Subject st: Mantel-Haenszel vs. clustered logistic - please help Date Fri, 23 May 2003 06:15:22 -0700 (PDT)

Dear all,

I am analyzing data from the 306 women at 4 outpatient
clinics in Oklahoma. Each woman was asked if they
performed monthly breast exams and other additional
data (covariates) such as race was collected. We would
like to characterize women according to these
covariates. I am concerned about the these women are
from different clinics and would like to take this
into account.

My first though was to performed a logistic regression
clustering on clinic. But I later though to use a
stratified analysis and compute a Mantel-Haenszel odds
ratio. However, I get very deferent results from these
methods and I am confused on which to use. Here is an
example:

nrace: 0=African American 1=Caucasian
breast-exam: 0=No 1=Yes

Mantel-Haenszel:
. mhodds   breast_exam nrace,by(clinic)

Maximum likelihood estimate of the odds ratio
Comparing nrace==1 vs. nrace==0
by clinic

-------------------------------------------------------------------------------
clinic | Odds Ratio        chi2(1)         P>chi2
[95% Conf. Interval]
----------+--------------------------------------------------------------------
CWC |   3.966102           7.27         0.0070
1.34348   11.70839
FN |   0.000000           1.26         0.2621
.          .
Freeway |   3.446154           4.76         0.0291
1.05511   11.25567
MB |   2.153846           0.40         0.5286
0.18671   24.84655
-------------------------------------------------------------------------------

Mantel-Haenszel estimate controlling for clinic

----------------------------------------------------------------
Odds Ratio    chi2(1)        P>chi2        [95%
Conf. Interval]

----------------------------------------------------------------
2.937339       9.71        0.0018
1.442772   5.980127

----------------------------------------------------------------

Test of homogeneity of ORs (approx): chi2(3)   =
4.12
Pr>chi2   =
0.2483

Clustered logistic:

. xi:logistic   breast_exam i.nrace,cluster(clinic)
i.nrace           _Inrace_0-1         (naturally
coded; _Inrace_0 omitted)

Logistic regression
Number of obs   =        306
Wald
chi2(1)    =       2.00
Prob
> chi2     =     0.1578
Log pseudo-likelihood = -160.29912
Pseudo R2       =     0.0186

for clustering on clinic)
------------------------------------------------------------------------------
|               Robust
breast_exam | Odds Ratio   Std. Err.      z    P>|z|
[95% Conf. Interval]
-------------+----------------------------------------------------------------
_Inrace_1 |   1.971711    .947687     1.41   0.158
.7686353    5.057856
------------------------------------------------------------------------------

Summary:

The raw OR:           1.97  (1.10,3.54) p= 0.0138
Mantel-Haenszel OR:   2.94  (1.44,5.98) p= 0.0018
Cluster logistic OR:  1.97  (0.77,5.06) p= 0.158

Regards,
Ricardo

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