Identification of diagnostic markers will avoid useless treatment with high dose corticosteroids in patients without GVHD Identification of prognostic markers will comfort the decision of a second-line treatment sooner than usually, ie: at GVHD onset. Indeed, the onset of a second-line treatment after a steroid-refractory GVHD varies from 3 to 21 days depending on clinical evolution of patients. If some prognostic markers are available at diagnosis, delay in second-line treatment can be shortened and the patient can consequently have an increased chance to response to an early treatment.