© 2019 Elsevier Ltd Background: Treatment of multiple myeloma with daratumumab (DARA)is increasing fast. Unfortunately, this antibody also attaches to red blood cells (RBCs)and mimics an autoantibody's panreactivity during pre-transfusion testing, necessitating specialized techniques, (e.g. dithiothreitol (DTT))for alloantibody detection. Many hospitals use a reference lab for such testing, increasing both cost and turn-around time (TAT). Herein, we compare the cost and TAT, pre and post-implementation of an in-house DTT protocol. Methods: We designed a validation of our in-house DTT protocol from Nov to Dec 2017 with full implementation on January 1, 2018. We retrospectively reviewed all pre-transfusion tests on DARA patients from Feb 2016 to April 2018, pre and post-implementation of in-house DTT testing. Descriptive statistics were used for patient demographics and a Student t-test was used to compare cost and TATs (pre and post-implementation). Results: We identified 49 patients on DARA treatment requiring transfusion. Samples from these patients were sent to the reference lab 104 times and were tested in-house 28 times. The average TAT for the reference lab was 19h25 m compared to our in-house TAT of 5h9m (an average time-savings of 14h16 m). We spent approximately $33,800 ($325 per test)for 104 reference lab samples versus $806.12 (˜$28.79 per test)for in-house testing of 28 samples. Conclusion: We provide an easily implementable DTT protocol for pre-transfusion testing community hospitals and beyond. As more monoclonal antibodies are developed and approved for clinical use, the lessons learned with DARA will expand to deal with interference from future targeted therapies.