1. Departments of Neurosurgery and Medicine, Vivian L. Smith Center for Neurologic Research, University of Texas Health Science Center at Houston Houston, Texas
2. Department of Pathology and Laboratory Medicine, University of Texas Health Science Center at Houston, Laboratory Services, Memorial Hermann Hospital Houston, Texas
3. Departments of Pediatrics and Medicine, University of Texas Health Science Center at Houston, and the Gulf States Hemophilia and Thrombophilia Center, Houston, Texas