[1] Queens Univ Belfast, Inst Clin Sci, Dept Surg, Belfast BT12 6BJ, Antrim, North Ireland
[2] Royal Victoria Hosp, Vasc Surg Unit, Belfast BT12 6BA, Antrim, North Ireland
[3] Royal Victoria Hosp, Dept Clin Biochem, Belfast BT12 6BA, Antrim, North Ireland