Bioequivalence and Bioavailability Forum

Replicate Designs & IntraSubj CV [General Statistics]

posted by randombadger – UK, 2011-04-28 15:02 (4738 d 19:15 ago) – Posting: # 6963
Views: 11,731

Hello all,

I have a 3 period, 2 treatment XO design and would like to calculate the intra-subject CV for the two treatments.

According to FDA guidance, I should use the following SAS code:

PROC MIXED DATA= cmax ;

  CLASSES armcd usubjid period treat ;

  MODEL LOG_PARM = armcd period treat / DDFM=KR;

  RANDOM treat/TYPE=FA0(2) SUB=usubjid G;

  REPEATED/GRP=treat SUB=usubjid;

  ESTIMATE 'B vs A' treat -1 1/CL ALPHA=0.1;

  LSMEANS treat/ cl alpha=0.1;

RUN;

however I see my colleagues are using the following:

PROC MIXED DATA= cmax ; 

   CLASS USUBJID period treat ARMCD ; 

   MODEL LOG_PARM = treat period ARMCD  /ddfm=KR;  

   RANDOM USUBJID(ARMCD) ;

   REPEATED/GRP=treat SUB=usubjid ;

   ESTIMATE "B vs A"  TREAT  -1 1 /cl alpha=0.1; 

   LSMEANS treat/ cl alpha=0.1;

RUN;

and I am finding the intra-subject CV's are quite different. I am a little confused regarding which RANDOM statement to use. Can anyone explain the differences and which statement is best to use?

My colleagues also included a carryover in the model but I believe the washout periods are long enough hence not required.

Thanks,
RB

Complete thread:

Replicate Designs & IntraSubj CVrandombadger 2011-04-28 13:02 [General Statistics]
- Replicate Designs & IntraSubj CV Helmut 2011-04-28 15:00
  - Replicate Designs & IntraSubj CV randombadger 2011-04-28 15:25
    - Replicate Designs & IntraSubj CV Helmut 2011-04-28 17:09
    - Inter-subject dance with the wolves d_labes 2011-04-29 11:33
      - How many subjects? jdetlor 2011-05-02 18:21
        
        G matrix d_labes 2011-05-03 08:26
        
        G matrix ElMaestro 2011-05-03 09:15
        
        G matrix d_labes 2011-05-03 09:51
        
        Results randombadger 2011-05-03 12:03
        
        Results - comments d_labes 2011-05-03 14:32
        
        Results - comments randombadger 2011-05-03 16:53
        
        Lost cents d_labes 2011-05-04 08:07
        
        G matrix ElMaestro 2011-05-03 14:16
        
        G matrix jdetlor 2011-05-03 19:37

Replicate Designs & IntraSubj CV [General Sta­tis­tics]

Complete thread:

Replicate Designs & IntraSubj CV [General Statistics]