The generalizability of participants in Veterans Affairs Cooperative Studies Program 474, a multi-site randomized cardiac bypass surgery trial

Objective: The Department of Veterans Affairs (VA) Cooperative Studies Program (CSP) initiated a multi-site randomized trial (CSP 474) to determine graph patency between radial artery or saphenous vein grafts in coronary artery bypass surgery (CABG). In this paper, we describe the study and compare participants' baseline characteristics to non-participants who received CABG surgery in the VA. Method: We identified our participants in the VA administrative databases along with all other CABG patients who did not have a concomitant valve procedure between FY2003 and FY2008. We extracted demographic, clinical information and organizational information at the time of the surgery from the databases. We conducted multiple logistic regression to determine characteristics associated with participation at three levels: between participants and non-participants within participating sites, between participating sites and non-participating sites, between participants and all non-participants. Results: Enrollment ended in early 2008. Participants were similar to non-participants across many parameters. Likewise, participating sites were also quite similar to non-participating sites, although participating sites had a higher volume of CABG surgery, a lower percentage of CABG patients with a prior inpatient mental health admission than non-participating sites. After controlling for site differences, CSP 474 participants were younger and had fewer co-morbid conditions than non-participants. Conclusions: Participants were significantly younger than non-participants. Participants also had lower rates of some cardiac-related illness including, congestive heart failure, peripheral vascular disease, and cerebrovascular disease than non-participants.