It is very important to perform irregular antibody screening to ensure safe and efficient red blood cell transfusion. In this study, we developed a new method to detect IgG class irregular antibodies by flow cytometry using anti-human IgG as a secondary antibody (Flow Cytometry Irregular Antibody Screening: FCM-SC). The mean fluorescence intensity ratio of the patient sample to negative sample (S/N) was estimated. The result was considered positive if S/N was greater than 1.7. For clinically significant antibodies like anti-E and anti-S, 12 out of 95 cases with Column Agglutination Technology (CAT) positive results were FCM-SC negative, and additional testing by PEG-IAT confirmed the negative results. 22 out of 29 cases that were anti-M and anti-Le^a antibody positive by CAT were FCM-SC negative, and additional testing by IAT without enhancement media revealed that all cases were negative. 9 out of 33 cases that did not show reaction specificity by CAT, such as by autoantibody and cold agglutination, were FCM-SC negative, and additional testing by PEG-IAT using plasma that had been treated with a reducing agent also showed negative results. These results suggest that FCM-SC is a useful method for detecting IgG class irregular antibodies and may be suitable for antibody screening.

The conventional prediction formula for CD34⁺ cell yield in peripheral blood hematopoietic stem cell harvest (PBSCH) is composed of peripheral blood CD34⁺ cell number, the processed blood volume, and body weight. In the present study, we proposed a novel prediction formula that includes the collection efficiency. The collection efficiency is defined by the following: the number of collected cells/the total number of CD34⁺cells in the processed blood. We evaluated the correlation between several factors that may affect the actual collection efficiency and the collection efficiency calculated using the above formula and the actual CD34⁺ cell number obtained by PBSCH. Among these, 32.5× (WBC/Hct) ^-0.364 showed the best correlation with collection efficiency. Therefore, we included it to represent collection efficiency in the prediction formula. These findings indicate that high WBC numbers leads to low CD34⁺ cell yield, presumably because the WBC sedimentation rate is low in the presence of high WBC numbers. Based on analysis of 48 PBSCH from 23 adult patients, the new prediction formula containing the collection efficiency showed higher prediction accuracy than the conventional prediction formula. This prediction formula allows prediction of the number of CD34⁺ cells before PBSCH and identification of the best conditions for PBSCH.

Introduction: Daratumumab (DARA) is a drug that specifically binds to CD38, which is abundantly expressed in myeloma cells, and has a therapeutic effect. CD38 is expressed on the surface of human red blood cells (RBCs), Irregular antibody screening and cross-matching using serum obtained after DARA administration have demonstrated panagglutination. In this study, we avoided the nonspecific reaction of DARA and studied the optimal concentration at which dithiothreitol (DTT) does not denature the clinically problematic antigen. Next, we studied storage of DTT treated cell reagents for screening.

Method: The DTT concentration and pH of phosphate buffered saline (PBS) used to dissolve DTT were adjusted, and the optimal conditions were set. In addition, serological and optical confirmation of the antigen reactivity of DTT treated RBCs were preformed after the preparation.

Result: The optimum concentration of DTT was 0.01 mol/l. When DTT was dissolved in PBS at pH 7.0 or higher, denaturation of CD38 was detected. At the same time, the Kell blood group antigen was also detectable, although its antigenicity was slightly reduced. With regard to the preservation of DTT treated RBCs, the antigenicity of the main antigen was detectable even at 28 days after DTT treatment.

Discussion: Preparation of DTT treated RBC reagents is too complicated to perform before each use. If RBC reagents for irregular antibody screening can be stored after DTT treatment, the work required in the laboratory for each DTT treatment can be reduced and efficiency of the test can be increased.

The true seroconversion ratio of individual antibodies after transfusion has not been elucidated. We are planning a multicenter prospective study to examine the seroconversion of antibodies after transfusion. Here, we report the results of our pilot study. We prospectively investigated the antibodies of patients who received an erythrocyte transfusion between March 2016 and September 2018. We simultaneously collected clinical data including sex, age, primary disease, previous transfusion history, amount of erythrocytes transfused (units) and the timing of examination after transfusion. Written informed consent was obtained from 307 cases before transfusion, and we conducted 267 examinations of antibodies in 263 cases after transfusion. Irregular erythrocyte antibodies were detected in 1.6% (5/307 cases; 1 for anti-C, 1 for anti-Jk^a, 1 for anti-E+c and 2 for anti-E) and 3.8% (10/263 cases) of cases before and after transfusion, respectively. New antibodies were detected in 1.9% (5 cases) of cases after transfusion. The mean amount of erythrocytes transfused (units) to those in whom new antibodies were detected (20±14 units, median 13 units) was significantly greater than that of all other patients (7±8, 4) (p=0.002). No safety or ethical problems were observed in this pilot study.

The Japanese Red Cross Society prepares Irradiated Frozen-Thawed Red Cells from two different sources: Red Blood Cells and Irradiated Red Blood Cells. The procedures used for preparation from the two sources differ by whether X-ray irradiation is performed before or after freezing and thawing. X-ray irradiation is widely known to exert some adverse effects on erythrocytes. Therefore, if the two preparative procedures result in differences in hemoglobin recovery, it would be advisable to choose the superior of the two procedures. We compared the quality of Irradiated Frozen-Thawed Red Cells prepared using the two different preparative procedures. We found no significant differences in hemoglobin recovery or hemolysis between the procedures. The potassium concentration in the supernatant was slightly different between the irradiation timings, but the difference exerts little adverse effect on blood transfusion samples.

Immediate treatment with percutaneous cardiopulmonary support (veno-arterial extracorporeal membrane oxygenation: VA-ECMO) should be considered for patients with circulatory collapse due to pulmonary thromboembolism. However, bleeding complications can occur during ECMO. A 65-year-old woman was admitted to our hospital with a chief complaint of sudden low back pain. VA-ECMO was immediately started as initial treatment because the patient underwent cardiopulmonary arrest just before arrival. We observed a defect in her pulmonary artery by contrast-enhanced CT and diagnosed her with pulmonary thromboembolism. She was admitted to the ICU, and subsequently underwent massive bleeding from the VA-ECMO catheter insertion site. Because the patient showed critical hypofibrinogenemia (e.g., 64mg/dl), she was administered 3g of fibrinogen concentrate. The fibrinogen supplementation reduced the bleeding and made it possible to remove the patient from ECMO after stabilization of hemodynamics. Anticoagulation treatment was started the day after the procedure, and she was extubated on the 6th day of admission, and discharged on the 23rd day. Hemorrhagic complications as a result of VA-ECMO, conducted for recovery from cardiopulmonary arrest, can be treated with early administration of fibrinogen concentrate to achieve hemostasis and improve patient condition.