From the Department of HaematologyLeyenburg Hospital, The Hague, the Netherlands; University Hospital, Albert-Ludwigs University, Freiburg, Germany; University Hospital Gasthuisberg, Leuven; Mont-Godinne UCL University Hospital, Yvoir; Hospital de Jolimont, Haine Saint Paul; and Hospital Notre-Dame Charleroi and Cliniques Universitaires Saint-Luc, Brussels, Belgium. (At 2000-03-01)