Fitting a reference group with exposure-outcome variable in proc logistic

ak2011 — Fri, 04 Sep 2020 02:20:54 GMT

Hello,

This is the corrected version of the last post. I am modelling refA not refB.

I finding the association between agents a1,a2,a3 and a4 exposures and lung cancer. Exposed = 1, unexposed =0. My ref. group(refA) is ids unexposed to any of the agents.

a. I am not sure whether my logistic regression model step 3b is right. I am modelling refA with lung-a1 association., then refA with lung-a2 association,etc.
b. Should the refA be considered as continuous or categorical(as I have done in step 3b of the model)?

Thanks in advance.

ak.




/* Logistic test ref group test*/
 data agents_exp;
input id$ a1 a2 a3 a4  lung$ 14-21 income 23-29;
datalines;
os1  1 0 0 1 ca case  45424
os2  1 1 0 0 ca case  52877
os3  0 0 0 0 pop cont 25600 
os4  1 0 0 1 pop cont 14888
os5  0 0 0 0 ca case  41036
os6  0 0 0 0 ca case  20365
os7  1 0 1 1 pop cont 16988
os8  0 0 0 0 ca case  100962
os9 1 0 1 0  pop cont 11230
os10 0 0 1 0 ca case  35850
os11 0 1 0 0 pop cont 28700
os12 0 0 0 0 pop cont 46320
os13 1 1 1 1 pop cont  24897
os14 0 0 0 0 pop cont  18966
os15 1 0 0 1 ca case  20540
os16 0 0 1 0 pop cont 150600
os17 1 1 1 1 pop cont  24897
os18 0 0 0 0 pop cont  17999
os19 0 0 0 0 pop cont  22540
os20 0 0 0 0 pop cont 158600
os21 0 0 0 0 pop cont 187365
os22 1 0 1 0 ca case  30580
;
run;

/*Step 1: Finding number of cases and controls unexposed to agents(a1,a2,a3 and a4)*/  
proc freq data= agents_exp(where=(sum(a1,a2,a3,a4)=0));
     tables lung;
title 'Table 1:Subjects unexposed to any of the 4 agents';
run;
/*Step 2:Using subjects unexposed to any of agents as a ref. group*/

proc sql;
create table t as 
  select
    id, a1, a2, a3,a4,lung,
    sum(a1,a2,a3,a4)=0 as refA
     from agents_exp
     ;
     quit;
     
   proc print data=t; 
   title 'Table 2: original variables and ref group';
   run;
   
    /*proc freq data=t;
    tables lung* refA lung*a1;
    title 'Table 3: freq of ca case and pop cont for ref group';
    run;*/

/*Step 3a: Finding odds ratio estimates for variables including ref.group*/ 

data logtest; set t;

if lung in ('ca case','pop cont');
run;

 
 /* Step 3b:*/
 proc logistic data=logtest;
class refA (param=ref ref ='0');
model lung(event='ca case') = a1 refA;  
Title 'Table 3b: Estimates for ref. group';
run;

1 OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;

73 /* Logistic test ref group test*/

74 data agents_exp;

75 input id$ a1 a2 a3 a4 lung$ 14-21 income 23-29;

76 datalines;

NOTE: The data set WORK.AGENTS_EXP has 22 observations and 7 variables.

NOTE: DATA statement used (Total process time):

real time 0.01 seconds

cpu time 0.00 seconds

99 ;

100 run;

101

102 /*Step 1: Finding number of cases and controls unexposed to agents(a1,a2,a3 and a4)*/

103 proc freq data= agents_exp(where=(sum(a1,a2,a3,a4)=0));

104 tables lung;

105 title 'Table 1:Subjects unexposed to any of the 4 agents';

106 run;

NOTE: There were 10 observations read from the data set WORK.AGENTS_EXP.

WHERE SUM(a1, a2, a3, a4)=0;

NOTE: PROCEDURE FREQ used (Total process time):

real time 0.23 seconds

cpu time 0.20 seconds

107 /*Step 2:Using subjects unexposed to any of agents as a ref. group*/

108

109 proc sql;

110 create table t as

111 select

112 id, a1, a2, a3,a4,lung,

113 sum(a1,a2,a3,a4)=0 as refA

114 from agents_exp

115 ;

NOTE: Table WORK.T created, with 22 rows and 7 columns.

116 quit;

NOTE: PROCEDURE SQL used (Total process time):

real time 0.02 seconds

cpu time 0.02 seconds

117

118 proc print data=t;

119 title 'Table 2: original variables and ref group';

120 run;

NOTE: There were 22 observations read from the data set WORK.T.

NOTE: PROCEDURE PRINT used (Total process time):

real time 0.49 seconds

cpu time 0.47 seconds

121

122 /*proc freq data=t;

123 tables lung* refA lung*a1;

124 title 'Table 3: freq of ca case and pop cont for ref group';

125 run;*/

126

127 /*Step 3a: Finding odds ratio estimates for variables including ref.group*/

128

129 data logtest; set t;

130

131 if lung in ('ca case','pop cont');

132 run;

NOTE: There were 22 observations read from the data set WORK.T.

NOTE: The data set WORK.LOGTEST has 22 observations and 7 variables.

NOTE: DATA statement used (Total process time):

real time 0.01 seconds

cpu time 0.02 seconds

133

134

135 /* Step 3b:*/

136 proc logistic data=logtest;

137 class refA (param=ref ref ='0');

138 model lung(event='ca case') = a1 refA;

139 Title 'Table 3b: Estimates for ref. group';

140 run;

NOTE: PROC LOGISTIC is modeling the probability that lung='ca case'.

NOTE: Convergence criterion (GCONV=1E-8) satisfied.

NOTE: There were 22 observations read from the data set WORK.LOGTEST.

NOTE: PROCEDURE LOGISTIC used (Total process time):

real time 0.56 seconds

cpu time 0.50 seconds

141

142

143 OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;

155

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Fitting a reference group with exposure-outcome variable in proc logistic