Programming the statistical procedures from SAS

Finding a cutoff value in multivariate logistic regression?

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Contributor
Posts: 22

Finding a cutoff value in multivariate logistic regression?

Hi, 

Need advice: I am trying to find cutoffs in a multivariate logistic regression model composed of a categorical predictor and several continuous variables:

 

PROC LOGISTIC DATA=work.sdcrossvalid OUTEST=_SNSP_EST; 

CLASS Bleed; 

MODEL Outcome(event='1')=

Age_yr_ 

PR 

Plt 

Sr_Creat 

AST 

ALT 

HCO3 

Lactate  

Bleed/ EXPB ;

 

To determine the cutoff value, I use the following formula:

 

X_value = (Logit - intercept)/(Sum of estimates of all predictor variables), as adapted from:

 

ref: Paper 231-2008 

A Macro For Getting More Out Of Your ROC Curve:

X_VALUE = (LOG(_PROB_/(1-_PROB_))-INTERCEPT)/&XVAR 

This paper only refer to a single continuous variable. What if you have several?

 

Is my denominator (Sum of estimates of all predictor variables) correct?

Grand Advisor
Posts: 9,447

Re: Finding a cutoff value in multivariate logistic regression?


If you have multiple levels for Y , that would lead you to two kind of logistic model:
1) cumulative logistic
2)generalize logistic


The cutoff value means nothing for these two kind of model.
If it is binary logistic model, CTABLE could give you a good vision to cutoff value.


proc logistic data=sashelp.class;
model sex=age weight height/ctable;
run;


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