Probabilities of grades 3 to 4 acute GVHD as stratified by the HCT-CI scores among 2985 recipients of allogeneic HCT. Patients with HCT-CI scores of 0, 1 to 2, 3 to 4, and ≥5 had 13%, 18%, 18%, and 24% probabilities, respectively, of grades 3 to 4 acute GVHD at 120 days after HCT.