Korean J Blood Transfus.  2023 Dec;34(3):171-181. 10.17945/kjbt.2023.34.3.171.

Daratumumab-Induced Interference in Flow-Cytometry Crossmatch and Resolving It by DTT Treatment

• Lee JK
• Jeong IH
• Kang N
• Jeong M
• Song HB
• Park JW
• Kang ES

• KMID: 2549679
• DOI: http://doi.org/10.17945/kjbt.2023.34.3.171

Abstract

Background
Daratumumab is a human monoclonal antibody targeting CD38 used widely in various related conditions. Caution is advised when interpreting the pretransfusion tests in daratumumab-treated patients because they may show nonspecific reactions with red blood cells. This paper provides experimental evidence for the false-positive interference phenomena induced by daratumumab in in-vitro and ex-vivo experiments and experimental support for resolving it using dithiothreitol (DTT).
Methods
Fifteen crossmatching pairs, four cardiac amyloidosis (CA) patients treated with daratumumab, and three healthy individuals were included. The flow cytometry crossmatch (FCMXM) was conducted with negatively selected T and B cells. After spiking the sera with 500 μg/mL daratumumab, the T and B cells were treated with DTT. The prospective FCMXM was conducted with the sera of CA patients treated with daratumumab. The CD38 expression levels in T, B, and NK cells were measured without and with a DTT or pronase treatment.
Results
Five hundred μg/mL of daratumumab spiking was sufficient to elicit a false positive effect in T cell FCMXM. In particular, the administration of 0.1 M DTT efficiently resolved the induced false positivity in flow cytometry. Moreover, DTT caused a decrease in the CD38 expression levels in T, B, and NK cells.
Conclusion
A typical therapeutic dose of daratumumab causes false-positive FCMXM, which was effectively addressed by a DTT treatment. Therefore, information about the patient’s medical condition and the use of immunotherapeutics, such as daratumumab, is needed, given its impact on diverse CD38-expressing cells.

Keyword

Cardiac amyloidosis; Daratumumab; Heart transplantation; HLA crossmatch; Flow cytometry