[1] Kings Coll Hosp NHS Fdn Trust, Dept Haematol Med, London SE5 9RS, England
[2] Kings Coll London, Fac Life Sci & Med, Mol Haematol, London SE5 9NU, England
[3] Kings Coll Hosp NHS Fdn Trust, Kings Thrombosis Ctr, London, England
[4] NIH, Sickle Cell Branch, Natl Heart Lung & Blood Inst, Bldg 10 CRC 5E-5142,10 Ctr Dr, Bethesda, MD 20892 USA