To ensure consistent analyses across individual datasets, a unified script was created using SAS (SAS Institute, Cary, NC) and R (http://www.r-project.org/). These scripts were developed and distributed following protocols comparable to Saccone et al. [Saccone et al., 2010a]. Briefly, participating groups held several planning conference calls to decide on the analytical model and scripts were written through collaborative efforts between SHS at the University of Colorado and SMH at Washington University in St. Louis. Individual analyses were carried out by each participating group and summary results returned to the coordinating group.
