Affiliation: | Paul Batty BSc(Hons) MBBS MRCP is a Specialist Registrar in Haematology at the Royal Surrey County Hospital, Guildford, Surrey, UK. Conflicts of interest: none declared; Graham Smith BSc MD FRCP FRCPath is a Professor of Haematology at the University of Surrey, Guildford and Consultant in Haematology at Frimley Park Hospital, Frimley, Surrey, UK. Conflicts of interest: none declared |