Colony-forming unit (CFU) assay has been used as a regulatory quality test to predict the lympho-hematopoietic reconstitution ability of hematopoietic stem cells in umbilical cord blood units. Nevertheless, the reliability of the test results cannot always be assured because a degree of subjectivity cannot be completely excluded from the criteria used to judge the type and number of colonies on microscopy. To overcome this issue, we evaluated the availability of an automated hematopoietic colony-counter system STEMvision^TM by analyzing the correlation between CFU assay results as determined by two experienced technicians and those determined by this automated system. Stable equipment operation was confirmed through accuracy control using a precision control plate with embedded artificial colonies. We found extremely strong correlations between any two of the three results for total colony numbers (rs > 0.92, p < 1.0 × 10^-39) and strong correlations between those for numbers of colony-forming unit-granulocyte/macrophage (rs > 0.79, p < 1.6 × 10^-20). These results suggest that this automated colony-counter system may give assay results comparable to those with conventional microscopic visualization, and accordingly warrant consideration for introduction as a standard CFU assay method that enables precision control.

Irregular erythrocyte antibody screening tests in patients treated with CD38 monoclonal antibodies lead to false-positive results because of the surface expression of CD38 on red-blood-cell reagents. We obtained false-positive results for blood samples from multiple patients using the automated pre-transfusion testing system IH-1000 (BIO-RAD) after testing a blood sample taken from a patient treated with daratumumab. This may have been caused by residual daratumumab-bound erythrocytes from the treated patient in the device. Such an occurrence may be more or less likely depending on conditions such as drug concentration and measurement sequence. Further verification is needed. Thus, caution is warranted when testing blood samples from patients on anti-CD38 antibody therapy using an automated pre-transfusion testing system.

A 71-year-old man developed hydronephrosis due to retroperitoneal lymph node swelling. He was diagnosed with follicular lymphoma (FL). However, FL transformed into a diffuse large B-cell lymphoma (DLBCL) during chemotherapy. He became refractory to chemotherapy and a large mass was formed in the right anterior chest. Therefore, he was referred to our hospital for an allogeneic hematopoietic cell transplantation (Allo-HSCT). After complete response/unconfirmed with radiation therapy for tumor, he received cord blood stem cell transplantation (CBT) following a reduced intensity conditioning regimen with fludarabin, melphalan, and total body irradiation and tacrolimus with mycophenolate mofetil for graft-versus-host disease (GVHD) prophylaxis. On day 16 after CBT, his neutrophil count engrafted. However, his lactate dehydrogenase levels (LDH) elevated, and on day 23, bone marrow biopsy showed mixed donor chimerism and fluorescence in situ hybridization demonstrated both MYC and BCR gene fusion. We discontinued immunosuppressants on day 26. His LDH level decreased, and bone marrow biopsy showed full donor chimerism on day 55 with no evidence of GVHD. We think the graft-versus-lymphoma (GVL) effect was induced only by discontinuation of the immunosuppressants. The methods of induction of GVL to treat early relapse of lymphoma after Allo-HSCT need to be developed in a future study.