Temple University Health System Philadelphia, Pennsylvania, United States
Background/Case Studies: Interference caused by daratumumab (DARA) in blood bank serology can be mitigated by treating reagent red blood cells (r-RBCs) with dithiothreitol (DTT). Because the conventional tube-based DTT treatment (DTT-T) is labor-intensive and delays transfusion, a previously described gel-based DTT-T (Gel-DTT) was evaluated as a streamline alternative. The primary aim was to identify the optimal DTT concentration and incubation conditions that effectively eliminate DARA interference while preserving clinically significant RBC antigens to allow the detection of alloantibodies.
Case: A 60 y/o male DARA patient presented with hemoglobin (Hb) of 6.3g/dL and a negative antibody screen by tube-DTT. Transfusion with immediate-spin crossmatch-K-neg-compatible RBC did not improve his Hb. The patient later developed acute hemolysis with dark urine, chest pain and dyspnea. Serologic testing was repeated using both tube and gel methods.
Study
Design/Methods: Anti-IgG gel cards and 0.8% screening and panel cells were used. The previously described Gel-DTT method involved adding 50µL of 0.8% r-RBCs to AHG gel columns, followed by 25µL of 0.04mol/L DTT, thorough mixing and incubation at 37°C for 15 minutes, then 25µL of patient's plasma was added and incubated at 37°C for the IAT. Initially, 11 previously tested samples were evaluated with both untreated and DTT-T r-RBCs for comparison. Based on the results, DTT incubation of r-RBCs was extended to 30 minutes for further assessment. Next, 34 samples from previously tested DARA patients without alloantibodies and 11 with alloantibodies were tested. To assess DTT's effect on the Kell (K) antigen, serial dilutions of anti-K-containing sera were tested against DTT-T K-positive r-RBCs.
Results/Findings: Treatment with 0.04mol/L for 15 minutes showed residual DARA interference, while extending incubation to 30 minutes eliminated interference in all tested samples, allowing detection of underlying alloantibodies such as anti-D, anti-K, anti-Fya, anti-Jka, and anti-S. Titration studies verified that K antigen integrity remained intact. In the case presented, the modified Gel-DTT method successfully removed interference and enabled identification of multiple alloantibodies, including anti-D, -E, and -Jkb, which had been missed by tube-DTT method. Conclusions: The modified Gel-DTT method effectively eliminates DARA interference while preserving K antigen on red cell membranes. This approach may eliminate the routine need for selecting K-negative units, reducing storage and quality control burdens, and enhancing turnaround time in pretransfusion testing. Furthermore, the increased sensitivity of Gel-DTT improves detection of underlying alloantibodies.
