Does anyone know of an approach for converting the OR from a multinomal, repeated measures logistic regression to a RR?
BACKGROUND
Performed an analysis to assess the treatment differences in severity (rated from 0 through to 5 each day) for both the primary time period (Week1, Day1-7) as well as across the trial (Days 1-28). The analysis was performed on each of the four outcomes using SAS GLIMMIX procedure:
PROC GLIMMIX DATA=dsn;
WHERE DAY LE 7; * LE 28 for the 1-28 analysis;
CLASS PATIENT TRT DAY;
MODEL SVRITY(ORDER=INTERNAL) = TRT DAY TRT*DAY
/ DIST=MULTINOMIAL LINK=CUMLOGIT;
RANDOM INT / SUB=PATIENT TYPE=type;
ESTIMATE 'Treatment 1 vs. 2' TRT 1 -1 / EXP;
RUN;
The UN (unstructured) covariance structure, as employed in the primary analysis, was used in the model for the assessment of severity for each of the four outcomes.
The data were primarily "0s" (none) across the trial; there was one outcome that was associated with statistically significantly lower severity - and the client is happy about this. The statistical output was, as expected, the Odds Ratio (OR) and the associated probability. The client wants this converted to a Risk Ratio (RR) because it is easier to understand.
I know any of the conversions are approximate, and the client is also aware of this. Any help would be appreciated.
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Janet McDougall
President
McDougall Scientific Ltd
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