Obsidian | Level 7

## 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?

3 REPLIES 3
Super User

## 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;

```
Pyrite | Level 9

## Re: Finding a cutoff value in multivariate logistic regression?

Thanks for sharing the code lines and this is what I intend to learn today.
Super User

## Re: Finding a cutoff value in multivariate logistic regression?

Here is a special macro for that purpose .
https://support.sas.com/kb/25/018.html
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