[1] Royal Infirm, Div Dev Med, Glasgow G31 2ER, Lanark, Scotland
[2] Univ Glasgow, Div Dev Med, Glasgow G12 8QQ, Lanark, Scotland
[3] Univ Glasgow, Dept Pathol Biochem, Glasgow G12 8QQ, Lanark, Scotland
[4] Univ Aberdeen, Ctr Healthcare Randomised Trials, Hlth Serv Res Unit, Aberdeen AB9 1FX, Scotland
[5] Ninewells Hosp, Dept Transfus Med, Dundee DD1 9SY, Scotland
[6] Royal Infirm, Dept Haematol, Glasgow G31 2ER, Lanark, Scotland