Overcoming pre-transfusion testing challenges with dithiothreitol to optimize transfusion support in multiple myeloma patients on daratumumab therapy

INTRODUCTION

Daratumumab (DARA) is an extraordinary drug used to treat multiple myeloma (MM), which is the second most common hematologic malignancy in the world. It is also used for immunoglobulin light-chain (AL) amyloidosis and various other hematologic malignancies.^[1] DARA is a human monoclonal antibody that specifically targets the CD38 surface protein, which is predominantly expressed on MM cells and, to a lesser extent, on lymphoid, myeloid, and a few non-hematopoietic cells.

DARA has transformed the treatment of MM patients by achieving progression-free survival and minimal residual disease.^[2] The disadvantage of DARA interference in serological testing is that it binds to CD-38 on test/reagent red blood cells, which can persist for up to 6 months even after stopping DARA.^[3,4] This results in an incompatible cross-match, a positive antibody screen, and identification panels exhibiting pan-agglutination, which can create a misleading impression of warm autoantibodies. This phenomenon may also obscure the presence of clinically significant alloantibodies, if they are present, as illustrated in [Figure 1a].^[5] This compromises transfusion safety, leading to extensive immunohematology workups and delays in reporting and providing packed red blood cells (PRBCs), particularly in cases with underlying alloantibodies.^[6] Dithiothreitol (DTT) 0.2 M is used to slice the CD-38 proteins on test or reagent red cells, which helps nullify any interference from DARA in the testing process. However, DTT may also destroy Kell antigens, so it is important to provide Kell-negative PRBCs for patients who are Kell antigen-negative.^[7]

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Figure 1:

(a) The mechanism by which Daratumumab interferes with pre-transfusion testing. (b) Immuno-hematological work-up of Case 1. (c) Immuno-hematological work-up of Case 2. (d) Immuno-hematological work-up Inference of Case 3. (e) Compatible cross-match following dithiothreitol treatment of packed red blood cell. CD: Cluster of differentiation, ICT: Indirect coomb’s test, DAT: Direct antiglobulin test, DARA: Daratumumab.

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A study conducted at our center involved three patients with MM. Pre-transfusion workups revealed problematic serological patterns due to DARA interference. Interference of DARA was eliminated by treating DTT with reagent red cells and donor red blood cells during antibody screening and cross-matching.

CASE SERIES

A summary of the clinical history of the three patients is presented in Table 1. A request for PRBC was submitted for these patients due to anemia. During pre-transfusion compatibility testing, the findings encountered are illustrated in Figures 1b-d, respectively. The blood grouping was done using a Gel card test (Tulip Diagnostics, Pvt. Ltd., Goa, India). The direct antiglobulin test (DAT) and auto-control were performed using an Antihuman globulin (AHG) gel card from Bio-Rad Laboratories, Inc., USA. An antibody screen was conducted using an AHG gel card with a three-cell panel (ID-DiaCell I-II-III, Bio-Rad Laboratories, Inc.). For antibody identification, we utilized an 11-cell panel (IDDiaPanel, Bio-Rad Laboratories, Inc., USA).

DISCUSSION

The interference of DARA during pre-transfusion testing in the first case led to an incompatible cross-match despite a pan-positive antibody screen and identification panel. This situation, combined with a positive direct antiglobulin test (DAT) and auto-control, could mimic the presence of a warm autoantibody or a drug-induced autoantibody. In addition, if the patient had a history of blood transfusions, pregnancy, or organ transplantation, there might also be an underlying alloantibody present. Similarly, in cases 2 and 3, the incompatible crossmatch was associated with a pan-positive antibody screen and antibody identification panel, but here, the DAT/auto-control was negative, so it presents a false picture of an alloantibody to a high prevalence antigen, which was supported by the fact that the patient had transfusion history. Hence, in such scenarios, unless the history of intake of anti-CD38 drugs is elicited or stated, there will be unnecessary delay in transfusion support due to work-up in the wrong, futile direction. The extracellular domain of human CD38 contains six disulfide bonds, which can be cleaved by DTT to release sulfhydryl groups, thereby preventing DARA interference.^[8] Other blood group system antigens altered include Lutheran, YT, JMH, LW, Cromer, Indian, Dombrock, and Knops; however, alloantibodies to these antigens are not common.^[9] In a case report by Rajput et al.,^[10] a patient with severe aplastic anemia scheduled for a hematopoietic stem cell transplant experienced an incompatible cross-match and pan reactivity in antibody screening tests (IAT). To address this, the patient underwent a desensitization protocol that included DARA, therapeutic plasma exchange, and immunoglobulins to reduce donor-specific anti-human leukocyte antigen antibodies. The interference in serological testing was effectively resolved using DTT.^[10]

In a study by Bub et al.,^[11] pan-reactivity was observed in indirect agglutination tests involving five hematology patients undergoing anti-CD38 drug therapy. This pan-reactivity was effectively negated when testing with DTT-treated reagent panel cells. Moreover, these cells could be stored for up to 15 days in Alsever’s solution, which helps save time in providing PRBC.^[11] This storage capability highlights the practical benefits of DTT treatment in transfusion services, particularly for patients undergoing anti-CD38 therapy.

Several strategies exist to eliminate unwanted serological interference caused by DARA during pre-transfusion testing, as summarized in Table 2. These findings collectively emphasize the utility of DTT as an indispensable tool in transfusion medicine for patients receiving anti-CD38 therapies. However, careful consideration of its limitations, such as Kell antigen denaturation, is necessary to ensure the safety and efficacy of transfusion practices. Sometimes, Kell antigen phenotyping in patients may be inconclusive due to recent transfusion history within the past 3 months in such patients. In such cases, genotyping is preferred, or the provision of Kell-negative PRBC may be made. In addition, the development of alternative methods to mitigate anti-CD38 interference without altering other blood group antigens may further enhance transfusion support in complex clinical scenarios.^[12-15]

CONCLUSIONS

DARA-related interference during pre-transfusion testing can complicate blood transfusion procedures, resulting in transfusion delays and potential safety risks. To address this interference, it is essential to implement DTT in the pre-transfusion workup. Establishing standard operating protocols and ensuring effective communication between departments is crucial before administering DARA.