1. Department of BiostatisticsUniversity of MichiganAnn Arbor, Michigan 48109U.S.A.
2. Department of MedicineUniversity of CaliforniaIrvine, Orange, California 92868U.S.A.
3. Institute for Clinical and Translational ScienceIrvine, California 92697U.S.A.
4. Department of MedicineUniversity of California DavisSacramento, California 95817U.S.A.
5. Department of BiostatisticsUniversity of CaliforniaLos Angeles, California 90095U.S.A.