Definitions
AA is characterized by pancytopenia and hypocellular bone marrow without
abnormal infiltrate or marrow fibrosis [6]. ABO blood type
compatibility between the donor and patient is crucial in blood group
systems [7]. ABO iso-group (match) refers to donors and patients
with the same ABO blood types [8]. The major ABO-incompatible group
consists of iso-agglutinins directed against donor red blood cell
antigens from type A, AB, or B donors to type O recipients. The minor
ABO-incompatible group consists of iso-agglutinins directed against red
blood cell antigens from type O donors to type A, B, or AB recipients.
Bidirectional ABO incompatibility, e.g., type A donor to type B
recipient, occurs when iso-agglutinins are present against both the
donor and patient red blood cell antigens. OS (overall survival) was
measured from the first day of therapy until death or the last
follow-up. GFFS (graft failure-free survival) was defined as survival
without grade III–IV acute GVHD (aGVHD), moderate-to-severe chronic
GVHD (cGVHD), or treatment failure, including death, primary or
secondary graft failure, and relapse [9]. Neutrophil engraftment was
defined as an absolute neutrophil count > 0.5 ×
109/L for three consecutive days. Platelet engraftment
was defined as an absolute platelet count > 20 ×
109/L for three consecutive days without transfusion.
Failure to achieve engraftment by day +28 was considered indicative of
low donor chimerism, and primary graft failure was assumed in such
cases. The diagnostic and classification criteria for aGVHD and cGVHD
were based on the Glucksberg-Seattle criteria [10,11].TA-TMA is
diagnosed and treated according to the criteria proposed by the IWG
(International Working Group)[12].