In the Post Coronary Artery Bypass Graft (POST CABG) clinical trial, the primary outcome is substantial worsening (i.e., narrowing of the lumen diameter) of the vein grafts upon comparison of the baseline and follow-up angiograms. The patients had one to five non-occluded vein grafts at entry, so there may be from one to five primary outcome responses per patient. A modified ratio estimate (MRE) statistic, as described previously by Zucker and Wittes, may be used to analyze data of this kind. In the present paper we propose a more powerful MRE statistic when the event rates and/ or intraclass correlations vary according to number of grafts per patient. We also adapt this statistic to the factorial treatment design of the POST CABG clinical trial.
Bibliographical noteFunding Information:
The authors wish to thank Dr. John M. Neuhaus and the journal referees for their helpful review of this paper. Support for the POST CABG clinical trial came from National Heart, Lung, and Blood Institute Contract No. NOl-HC-75076.
- Controlled clinical trial
- Coronary artery bypass grafts surgery
- Ratio estimate