1. Department of Health Services Research, Management and Policy, University of Florida, P.O. Box 100195, Gainesville, FL 32610, USA
2. Department of Community Health and Family Medicine, University of Florida, P.O. Box 100237, Gainesville, FL 32610-0237, USA
3. Department of Health Sciences, University of Leicester, 22-28 Princess Road West, Leicester LE1 6TP, UK
4. Department of Family and Community Medicine, Texas Tech University Health Science Center at El Paso, 9849 Kenworthy Street, El Paso, TX 79924, USA
5. Division of Blood Disorders, CDC, National Center on Birth Defects and Developmental Disabilities, Mail-Stop E87, 1600 Clifton Road, Atlanta, GA 30333, USA