[1] RNHRD, Dept Rheumatol, Bath, Avon, England
[2] North Bristol NHS Trust, Dept Rheumatol, Bristol, Avon, England
[3] Univ Bath, Dept Pharm & Pharmacol, Bath BA2 7AY, Avon, England
[4] UCL, Inst Child Hlth, Dept Rheumatol, London, England
[5] Univ Bath, Dept Math, Bath BA2 7AY, Avon, England