Hi all
I was wondering if you were kind enough to give me a short advice on a statistical query i have.
I have a sample of 15 children with a rare medical condition on treatment with a special diet. During the treatment course I have serial measurements (4 measurements at 0, 15, 30, and 60 days of treatment) of a disease marker. For some of these children (n=6) the disease activity improved and for the rest 9 did not at the end of treatment (60 d).
The research question I have to address is whether the percent change from baseline of the disease marker at 15 and/or 30 days can predict the clinical outcome at 60d (disease improvement or not improvement).
What I did is:
I calculated the %change from baseline at 15 and 30 days and I applied a binary logistic regression model for each time point seperately . The response is (disease improvement or not improvement) and the predictor % percent change of the inflammatory marker concentration at 15 and 30 days.
Now although I am getting "a test of all slopes are zero" which is very significant (p<0.0000001) the predictor (%change) is not (p=0.177)! Moreover when I did Mann Whitney test for difference in %change at 30day between patients who achieved clinical remission and those did not I got a p-value <0.0001.
I am a bit mixed up whether the %change at 30 days is an actual predictor of clinical outcome (disease remission) or not. Any advice on that?
I attach/uploaded a word document with the minitab analysis
I am looking forward to hearing from you
Kostas
I was wondering if you were kind enough to give me a short advice on a statistical query i have.
I have a sample of 15 children with a rare medical condition on treatment with a special diet. During the treatment course I have serial measurements (4 measurements at 0, 15, 30, and 60 days of treatment) of a disease marker. For some of these children (n=6) the disease activity improved and for the rest 9 did not at the end of treatment (60 d).
The research question I have to address is whether the percent change from baseline of the disease marker at 15 and/or 30 days can predict the clinical outcome at 60d (disease improvement or not improvement).
What I did is:
I calculated the %change from baseline at 15 and 30 days and I applied a binary logistic regression model for each time point seperately . The response is (disease improvement or not improvement) and the predictor % percent change of the inflammatory marker concentration at 15 and 30 days.
Now although I am getting "a test of all slopes are zero" which is very significant (p<0.0000001) the predictor (%change) is not (p=0.177)! Moreover when I did Mann Whitney test for difference in %change at 30day between patients who achieved clinical remission and those did not I got a p-value <0.0001.
I am a bit mixed up whether the %change at 30 days is an actual predictor of clinical outcome (disease remission) or not. Any advice on that?
I attach/uploaded a word document with the minitab analysis
I am looking forward to hearing from you
Kostas