1. Imaging Science and Biomedical Engineering (K.A.W., J.E.A.), University of Manchester, Manchester M13 9PT, United Kingdom
2. Central Manchester Primary Care Trust (G.D.), Longsight Health Centre, Longsight, Manchester M13 0RR, United Kingdom
3. Vitamin D Research Group (J.L.B.), Medicine, University of Manchester, Manchester Royal Infirmary, Manchester M13 9WL, United Kingdom
4. Health Methodology Research Group (S.A.R.), University of Manchester, Manchester M13 9PT, United Kingdom
5. Novotec Medical GmbH (R.R.), D-75172 Pforzheim, Germany
6. Department of Paediatric Medicine (Z.M.), Saint Mary’s Hospital for Women & Children, Central Manchester & Manchester Children’s Hospitals National Health Service Trust, Manchester M13 0JH, United Kingdom