Definitions
The date of stem cell infusion was defined as day zero. Lymphocyte recovery was classified based on the ALC in peripheral blood obtained using complete blood count routinely performed on D+30, D+100 and D+180. Based on previous studies, lymphocyte recovery was defined as ALC≥300/μL for D+30, ALC≥500/μL for D+100, and ALC≥750/μL for D+180.10–12
Flow cytometry immunophenotyping of peripheral blood was used to assess CD3+CD4+, CD3+CD8+, CD16+CD56+ and CD19+ counts obtained 100 days after HSCT (±14 days). Recovery of subtypes CD3+CD4+, CD3+CD8+ and CD19+ were classified as absolute counts ≥200/μL and ≥150/μL for CD16+CD56+​. Thus, patients with absolute counts below the ​​described values were classified as not recovered based on previous studies.13,14
Engraftment was confirmed through an absolute count of neutrophils and platelets in peripheral blood, and the chimerism test using polymerase chain reaction (PCR) short tandem repeat detection of donor DNA. Neutrophil engraftment was considered as the first day of 3 consecutive days when neutrophil count ≥500/μL, and platelet engraftment was the seventh day with platelet count ≥20 000/μL unsupported by transfusion. 15 CMV infection was screened using pp65 antigenemia or DNA detection by quantitative PCR assay. Acute GvHD was defined using standard clinical and laboratorial criteria and classified as grade 1-4, considering only aGvHD ≥grade 2 as clinically significant.16 Chronic GvHD was not analyzed due to the reduced number of cases up to D+180. Among hematological malignancies, disease phase was defined as early in case of first or second remission, and advanced in case of third or fourth remission, or active disease at the time of HSCT.