1. Department of Emergency Medicine, Stanford University School of Medicine, Stanford, CA.
2. Department of Pediatrics, Marshall University, Joan C. Edwards School of Medicine, Huntington, WV.
3. Stanford Health Care, Stanford, CA.
4. University of California—San Francisco School of Medicine, San Francisco, CA.
5. Quantitative Sciences Unit, Stanford University, Stanford, CA.
6. Department of Epidemiology and Biostatistics, University of California—San Francisco, San Francisco, CA.