1 Jesse Brown VA Medical Center, Chicago, IL 60612, USA; Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
2 Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois at Chicago, Chicago, IL 60612, USA.
3 Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois at Chicago, Chicago, IL 60612, USA; Biostatistics Shared Resource, University of Illinois Cancer Center, Chicago, IL 60612, USA.
4 Jesse Brown VA Medical Center, Chicago, IL 60612, USA; Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA. Electronic address: jkt@uic.edu.