[1] Salford Royal Hosp Fdn Trust, Dept Renal Med, Salford, Lancs, England
[2] N Manchester Grp Hosp, Dept Cardiol, Manchester M8 6RB, Lancs, England
[3] Ealing Hosp NHS Trust, Dept Cardiol, London, England
[4] Portsmouth Hosp NHS Trust, Dept Cardiol, Portsmouth, Hants, England
[5] Univ S Manchester Hosp, Dept Cardiol, Manchester M20 8LR, Lancs, England
[6] Univ Minnesota, Minneapolis, MN USA
[7] Minneapolis Med Res Fdn Inc, Nephrol Analyt Serv, Chron Dis Res Grp, Minneapolis, MN USA
[8] Manchester Royal Infirm, Dept Renal Med, Manchester M13 9WL, Lancs, England