data lows;
  attrib test length=$5
         date format=date.;
  pat=1;date='1jan01'd;test='hgb';value=1;output;
                       test='plats';value=2;output;
  pat=1;date='2jan01'd;test='hgb';value=3;output;
                       test='plats';value=4;output;
  pat=2;date='1jan01'd;test='hgb';value=5;output;
                       test='plats';value=7;output;
  pat=2;date='2jan01'd;test='hgb';value=6;output;
                       test='plats';value=8;output;
run;

%macro demo;

  proc transpose data=lows prefix=lo_ out=xlows;
    by pat date;
    id test;
  run;

  /* Put var names into an array */
  proc contents data=xlows noprint out=xlows_c;
  run;

  data _null_;
    set xlows_c end=finish;
    where name eq: 'lo_';
    call symput('VN'!!compress(putn(_n_,'6.'))
               ,name);
    if finish then call symput('VNTOTAL',putn(_n_,'BEST.'));
  run;
  %put vn1=&vn1;
  %put vn2=&vn2;
  %put vntotal=&vntotal;

  /* Now do the processing */
  data fail;
    set xlows;
    %do i=1 %to &vntotal;
      %put &&&vn&i;
      %if %substr(&&&vn&i,1,3) eq lo_ %then
      %do;
        put 'it is a low limit value';
      %end;
    %end;
  run; 

%mend demo;

options mprint NOmlogic;
options validvarname=v7; /* or v6 */
%demo;