GVHD classification after the NIH consensus conference. The current consensus is that clinical manifestations and not the time after transplantation determine whether the clinical syndrome is considered aGVHD or cGVHD. Retrospective and prospective studies reported wide ranges in the incidences of “late aGVHD” (3%-48%) and “cGVHD overlap” (13%-82%); more prospective cohort studies are needed.