(P-MG-2) Cost Benefit of In-House Dithiothreitol Testing Implementation

Daratumumab (anti-CD38) is a monoclonal antibody that binds to the CD38 protein expressed on some immune and cancer cells, including the plasma cells in multiple myeloma (MM). However, small amounts of CD38 are also expressed on red blood cells (RBC) and daratumumab therapy can mask alloantibodies when performing the antibody screen (and antibody identification) during pretransfusion testing. One method to eliminate the anti-CD38 reactivity on RBC is by denaturing the CD38 protein using dithiothreitol (DTT).

Study

Design/Methods:

To reduce turn-around-time (TAT) and potentially reduce the cost of send-out reference laboratory (SRL) testing, our institution (a quaternary care teaching hospital) implemented in-house DTT testing. At the time of implementation, we also modified the frequency of repeat antibody identification (ABID) testing and discontinued prophylactic RBC antigen matching except for providing K negative RBC as the K antigen is denatured by DTT treatment).

After ten months of in-house DTT testing, an analysis was performed to determine the potential cost savings by:

Calculating the cost of SRL ABID testing based on the previous process of repeat testing every 3 months.

Calculating the cost of DTT tests performed in-house, including the cost of all reagents (screening cells for tube testing, 0.2M DTT, RBC storage solution, and antisera for controls) and the cost of technologist’s time.

Calculating the cost of antigen negative RBCs that would have been purchased based on the previous process of prophylactic antigen matching.

Comparing the cost post DTT implementation to the potential cost if DTT testing was not implemented.

Results/Findings:

In the ten months since DTT testing was implemented, 165 tests were performed on 79 patients. Review of these cases revealed that 85 of these samples would have needed SRL workups at a cost of $44,271.11 (first time ABID cost $535.97, follow up investigation $321.58).

This was significantly higher than the $13,193.03 (or $79.96 per DTT test) estimated for in-house DTT testing (which included: the cost of technologist time $6,160, 14 sets of screening cells used for DTT testing $1,263.22, 0.2M DTT reagent $1,187.46, the RBC storage solution $4,044, and the D and K antisera used for controls $538.35).

The in-house DTT testing also allowed for the elimination of prophylactic RBC antigen matching for patients that would have resulted in an additional cost of $186,872.15.

Conclusions:

Implementation of in-house DTT testing can result in significant cost savings at institutions caring for many MM patients. Over ten months, we estimate that our institution saved over $200,000 due to the in-house DTT testing implementation.