1. Centre for Health Economics; University of York; York; YO10 5DD; U.K
2. School of Medicine; Pharmacy and Health; Durham University; Stockton-on-Tees; TS17 6BH; U.K
3. Academic Unit of Dermatology Research; University of Sheffield Medical School; Sheffield; S10 2RX; U.K
4. Metaxis Ltd; Curbridge; OX29 7NT; U.K