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
(standard errors adjusted
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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