Dear all, I have to perform a trt comparison by visit using a logistic regression model with repeated measures including factors for treatment and country/region as well as visit as repeated measure. In addition, the least-square means including 95% confidence intervals of both trt groups will be splotted versus time. So, I have started to work on a modeling using proc genmod. * USUBJID is the subject identifier. * Dependent variable = RESPFN is coded 1 for responder and 0 for non-responder * TRT01PN is coded 0 for PBO, 1 for Active * AVISITN is the numeric version of AVISIT (BASELINE, WEEK 1, WEEK 2, ..., WEEK 24, ..., WEEK 52) - Note that: AVISITN doesn't reflect the real time. For example, BASELINE is coded 20, WEEK 1 is coded 30, WEEK 2 is coded 40, but: WEEK 4 is coded 50 (not 60). Should I re-create a new numeric variable containing the real time ? The responder status is asessed at each visit for all patients. * COUNTRY contains to country code. We can have up to 28 countries. It represents a lot of categories. We may not need this variable at the end - since it may have a lots of cats, which may cause issues in the modelling. Could you please let me know what do you think of the code below ? Also : - Which type of working correlation matrix would you use? - I'm not sure that the inclusion of AVISITN in the proc genmod is really good (I've seen some examples on SAS documentation with some visit variables, but the variable was not included in the proc genmod). But, if I do not include it in my model, I don't see how I could estimate OR at each visit? ods output estimates=ESTIMtest ; proc genmod data = efftab descending ; class usubjid trt01pn avisitn country ; model respfn = avisitn trt01pn country / nointdist=bin link=logit ; repeated subject=usubjid / withinsubject=avisitn ; estimate "OR Active versus PBO at WEEK 1" trt01pn -1 1 avisitn 30 / exp ; run ; I'm working on SAS version 9.3. It would be great if you could provide me with your input on this statistical analysis! I have started to work on it since a while without managing to go very much further. Thanks so much in advance for your help, Best regards, Violaine
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