1. Rheumatology Research Unit, Addenbrooke's Hospital, Cambridge, CB2 2QQ, U.K.
2. Department of Medical Biochemistry, University of Calgary, Alberta, Canada T2N 4N1
3. Department of Medical Genetics, University of Calgary, Alberta, Canada T2N 4N1
4. University Clinical Biochemistry, Southampton General Hospital, Southampton SO16 6YD, U.K.
5. University Medicine, Southampton General Hospital, Southampton, SO16 6YD, U.K.