[1] Regina Apostolorum Hosp, Dept Med Sci, I-00041 Albano Laziale, Italy
[2] Univ Cambridge, Dept Publ Hlth & Primary Care, Cambridge, England
[3] Johns Hopkins Univ, Div Gen Internal Med, Baltimore, MD USA
[4] Univ Roma La Sapienza, Dept Publ Hlth Sci, Rome, Italy
[5] Inst Child Hlth, Mol Immunol Unit, London, England
[6] Barts & London Queen Marys Sch Med & Dent, Dept Haematol, London, England
[7] Tor Vergata Univ Hosp, Dept Hematol, Rome, Italy
[8] Cornell Univ, New York Presbyterian Hosp, Weill Med Coll, Div Hematol Oncol,Dept Pediat, Ithaca, NY 14853 USA