1. Prepared by Victoria Costa, MD and reviewed by Lorraine N. Blagg, MA, MLS(ASCP)SBB

Clinical Vignette

An adult with a history of multiple myeloma on daratumumab (last received a few weeks ago) and newly diagnosed acute leukemia was admitted and has been receiving RBC and platelet transfusions. The patient's course has been complicated by bleeding and concern for disseminated intravascular coagulation. The patient was also found to have massive splenomegaly. A transfusion reaction was reported due to lack of appropriate increment with RBC transfusion in the absence of signs and symptoms of bleeding.

Hgb 6.5 g/dL and platelets 7 K/cu mm
- 1 platelet unit 0500-0545
- 1st RBC unit 0600-0830

Hgb 6.7 g/dL (0945), Hgb 6.3 g/dL (1430)
- 2nd RBC unit 1500-1730

Hgb 5.9 g/dL (2100)
- 2nd platelet unit 1800-1900
- 3rd platelet unit 1900-2000

CT scan of the abdomen and pelvis was performed and was without evidence of bleeding. Laboratory evaluation for hemolysis showed mild elevation in bilirubin, down-trending LDH, detectable haptoglobin, and peripheral smear without evidence of schistocytes or spherocytes. Urinalysis showed small hemoglobin pigment and few RBCs. The patient was transfused multiple units of red blood cells and platelet transfusions during this admission and during prior admissions without issue and has no history of transfusion reactions.

Transfusion reaction work-up:

Clerical check: Appropriate

Pre-and-post ABO/Rh: O positive (pre) /O positive (post)

Unit ABO/Rh: O positive

Antibody screen: Antibody screen is positive with pre and post specimen.
The post-transfusion sample DTT-treated screen was positive on first testing. Antibody ID panel in solid phase red cell adherence (SPRCA) and in gel column agglutination showed no apparent alloantibodies. Repeat DTT-treated screen was done and was negative.

Pre and post crossmatches: Incompatible, patient is approved to get incompatible K1- RBC's.

Pre and post DAT: Positive; DAT battery for both specimens positive for polyspecific and IgG; eluate is negative.

In initial discussions of this work-up with the clinical team, they expressed concern about incompatibility of cross-matches since the patient stopped receiving daratumumab a few weeks ago, and questioned possibility of an alloantibody.
How long does daratumumab-associated reactivity persist after the last daratumumab administration?