Case 81

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

Clinical vignette
An adult presents to the oncology clinic, where they are being treated for an adenocarcinoma. Labs show a hemoglobin of 4.9 g/dL and thepatient is urgently transfused with one unit of packed red blood cells. At the end of the transfusion, they develops a fever, chills, and rigors. A transfusion reaction work-up is initiated. Of note, the patient has previous history of red blood cell transfusion, most recently three weeks ago.
Plasma: grossly hemolyzed
Transfusion Line: slightly hemolyzed

Question: How can the Direct Antiglobulin Test (DAT) be negative if the antibody screen is positive?