Hey everyone!

I'm trying to analyse my bachelor's thesis data in SPSS, but I'm not entirely confident I'm using the right methods. Could you please have a look and possible point me in the right direction? That would be amazing, since I've been stressing out about for a while now.

My research has 3 parts:

1)
Compare medication group (using drug A) to a control group.
I want to assess loss in renal function over 5 years time of using drug A. I measure GFR (for renal function) at t=0 and t=5 years, so I have 2 GFR values per subject. I also have a number of covariates (time of chronic infection in days, certain compound serum levels, and two categorical variables [e.g. whether or not they are diabetic]).

I was thinking of using Analyze > General Linear Model > Repeated Measures. However, I can't use string variables (e.g. diabetes) as a covariate, and I'm not sure which model/contrast to choose!

2)
Exactly the same as above, but this time I include concurrent drug B use by introducing a different way of grouping:
Group 0 = Uses drug A, does not use drug B
Group 1 = Uses drug A and drug B
Group 2 = Uses drug A, using drug B (before GFR measurement 1) but not during drug A

Group 3 = Not using drug A or B (control group)
Group 4 = Not using drug A, using drug B
Group 5 = Not using drug A, using drug B (before GFR measurement 1)

I was thinking of using the same system as the one above.

3)
Here I look at a group of people that quit drug A for whatever reason, to assess their renal function.

I have people that quit at different times (sometimes after 1 month, sometimes 3 years). I have:
1) a GFR measurement before starting drug A
2) a GFR measurement right before quitting drug A
3) a GFR measurement after quitting drug A

I want to see whether there is a significant loss in GFR during use of drug A, compared to the period after quitting.

Again, I was thinking of using the same model, but this time without a grouping factor, since I don't have a control group for this part of the research.

Any tips, will help, I'm sorry for the long story but I wanted to explain the case fully! If you have a completely different method/model in your head when reading the text, please let me know, I really want to learn more about biostats and SPSS.

Best regards,

Scoltey