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SAS Code for the First Step

The joint model formulated in (12.6) can be fitted using the SAS procedure MIXED in the following way:

proc mixed data=dataset covtest; class endp patid trial;

model outcome = endp endp*treat*trial / S noint; repeated endp / type=un subject=patid(trial); ods output solutionF=eb CovParms=covar; run;

Note that the two-way interaction term endp*treat is dropped from the MODEL statement and instead we use the variable endp; as a result, a common intercept is fitted to the two endpoints. The panel in Figure 12.12 shows the parameter estimates for the first-stage model. The individual-level surro-

FIGURE 12.10

Age-Related Macular Degeneration Trial. Estimation of trial-level surrogacy using a two-stage model. Trial-specific treatment effects obtained from the reduced fixed-effects model. Circle areas are proportional to trial size.

gacy measure can be estimated using the residual covariance matrix shown in Figure 12.12,

The second-stage model, from which trial-level surrogacy is estimated, can be fitted in the same way as in Section (12.3.1).

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SAS Code for the First Step
Although not visible to the users, the analysis implemented in the %CONTCONTFULL macro is based on procedure MIXED. In this section we discuss in more detail the implementation of the joint model specified in (12.1) in SAS. Using procedure MIXED, the following code can be used to fit the joint model...
(Applied Surrogate Endpoint Evaluation Methods with SAS and R)
SAS Code for the Second Step
The second-stage model, from which trial-level surrogacy is estimated, is based on procedure REG. proc reg data=secondstage; model true=surrinterc surrogate; weight n; ods output FitStatistics=rsq; run; Here, true is the parameter estimate for the treatment effect on the true endpoint (/3j), surrinterc,...
(Applied Surrogate Endpoint Evaluation Methods with SAS and R)
SAS Code for the Full Mixed-Effects Model
The full mixed-effects model can be fitted using procedure MIXED. Possible code is given by proc mixed data=dataset covtest; class endp patid trial; model outcome = endp endp*treat / solution noint; random endp endp*treat / subject=trial type=un; repeated endp / type=un subject=patid(trial); ods output...
(Applied Surrogate Endpoint Evaluation Methods with SAS and R)
SAS Code for the Reduced Mixed-Effects Model
The SAS code to fit the reduced mixed-effects model is: proc mixed data=dataset covtest; class endp patid trial; model outcome = endp endp*treat / solution noint; random endp*treat / subject=trial type=un; repeated endp / type=un subject=patid(trial); ods output solutionF=fix CovParms=covar SolutionR=eb;...
(Applied Surrogate Endpoint Evaluation Methods with SAS and R)
SAS Code for the First-Stage Model
The Cox proportional hazard model formulated in (12.18) can be fitted using SAS procedure PHREG. proc phreg data=firststage covs(aggregate) covout outest=mat; class center endpoint/param=glm; model outcome*status(0)= endpoint*treat*center; strata center endpoint; id patid; run; It is assumed that there...
(Applied Surrogate Endpoint Evaluation Methods with SAS and R)
SAS Code for Trial-Specific KM Estimates (at a Given Time Point)
...
(Applied Surrogate Endpoint Evaluation Methods with SAS and R)
SAS Code for the First-Stage Model
In this section we discuss the implementation of the first-stage model using SAS procedure GLIMMIX. Note that the macro %NORMALBIN uses the same implementation, although it is not visible for the user. The joint model (12.41) is fitted using the following code: proc glimmix data=norbin; class patientid...
(Applied Surrogate Endpoint Evaluation Methods with SAS and R)
SAS Code for the First-Stage Model
The SAS code to fit the reduced fixed-effects model formulated in (12.44) can be written as follows: proc glimmix data=binbin; class patientid endp trial; model response(event='1') = endp endp*treat*trial / noint s dist=byobs(endp) link=byobs(lin) cl; random _residual_ / subject=patientid type=un cl;...
(Applied Surrogate Endpoint Evaluation Methods with SAS and R)
Step 3: Coding
Words, phrases, lines, sentences or paragraphs pertaining to the themes and categories were coded. Coding, as a main technique in content analysis, is defined as the process of examining qualitative raw data in the form of words, phrases, sentences and paragraphs that are assigned (Strauss, 1987; Strauss...
(The Life and Creative Works of Paulo Coelho : A Psychobiography from a Positive Psychology Perspective)