PS Match and Mahalanobis Distance

[SG1993]

Hi, 

I am running the following code and am getting the error that "The variable Gender in the STAT=MAH option is in the class list". 

proc psmatch data=drugs region=cs;

   class Drug Gender;

   psmodel Drug(Treated='Drug_X')= Gender Age BMI;

   match method=greedy(k=1) 

         distance=mah(lps var=(Age BMI Gender)) caliper=0.2

         stat = lps

         weight=none;

   assess lps var=(Gender Age BMI);

   output out(obs=match)=OutEx7 matchid=_MatchID;

run;

I wanted to see of there was a way to include categorical variables in the Mahalanobis distance calculation in the above procedure. Any suggestion would be really appreciated. 

Thanks! 

[mkeintz]

If GENDER were taken out of the CLASS statement, and if gender were coded as, say 0 and 1, wouldn't it then serve your purpose?  I believe that's all you would need to account for the confounding of GENDER with AGE & BMI in assignment of DRUG.