1. Department of Medicine, Walter Reed National Military Medical Center , Bethesda, MD 20889 , USA
2. Department of Biostatistics, University of Alabama at Birmingham , Birmingham, AL 35233 , USA
3. Department of Medicine, University of Vermont Larner College of Medicine , Burlington, VT 05401 , USA
4. Department of Epidemiology & Biostatistics, Dornsife School of Public Health, Drexel University , Philadelphia, PA 19104 , USA
5. Department of Medicine, University of Mississippi Medical Center , Jackson, MS 39216 , USA
6. Department of Pathology and Laboratory Medicine, University of Vermont Larner College of Medicine , Burlington, VT 05401 , USA