I need help with a matched case-control study. I had an outcome of interest 'TMC' and matched 1 case of 'TMC' to 2 controls by age. Now, I want to analyse with SAS to see whether variables of interest are different (2-sided) in cases vs. controls. The data is non-parametric, non-symmetrical for the most part.
'TMC' is the condition (case=1, control=0), 'daysadmit' is the continuous variable
For the continuous variables, I used the following code:
PROC GLM DATA = descriptive ;
CLASS match tmc ;
MODEL daysadmit = tmc match(tmc);
Is this correct? Do I need to look at the p-value for match(tmc), or do I need that nested variable in there at all? Or, is sufficient to have 'match' in the class statement and only have daysadmit=tmc as the model?
Also, is there any value to putting in this statment:
TEST H = tmc E = match(tmc);
For the categorical variables I used:
if TMC=0 then status=2;
if TMC=1 then status=1;
if TMC=1 then censor=1;
if TMC=0 then censor=0;
Where I made status=1 controls, status=2 cases (of toxic megacolon), censor=0 controls, censor=1 cases.
The problem here is that the numbers are strange. I want to see whether the frequency of a bunch of variables is different in the case group from the control group. The the predictor variable listed above ('fever'), 90% of the case group ('TMC') had fever while 25% of the control group had fever. Using the above program, I get a p of 0.026. With leukocytosis 'leuko' as the predictor, 80% of the case group had leukocytosis while 5 % of the control group had leukocytosis. It looks like it should be significant, but I get a p value of 0.996. HELP! Can someone help me with what to do?
You have one case matched with two controls - from your description I understand the variable "match" shows who is matched with who, and the variable "TMC" shows who is the case and who is the control.
If your variable of interest "daysadmit" is approximately normal, then to compare cases and controls run the following code:
proc mixed data=descriptive;
class match TMC;