The symptom most commonly associated with a DHTR is an unexplained decrease in hemoglobin. Patients may also present with fever and jaundice. Hemolysis occurs slowly and is primarily extravascular. Unlike an acute hemolytic transfusion reaction (AHTR), hemoglobinuria, acute renal failure, and disseminated intravascular coagulation (DIC) are not generally seen. Many delayed reactions may go unnoticed as patients may not report the symptoms to their physicians unless they are severe.
Serologic findings include a positive direct antiglobulin test (DAT) and/or a positive antibody screen in post-transfusion testing. In many cases, the physician will send a request for an additional transfusion because of the decreased hemoglobin levels and not suspect a DHTR. The positive antibody screen will trigger an investigation, including antibody identification. The DAT may have a mixed field appearance because of the antibody-sensitized transfused red cells and the non-sensitized patient red cells. Segments from the donor unit can be tested for the offending antigen once the antibody has been identified.
Antibodies most often reported as the cause of DHTR are anti-Jka and anti- Jkb. Other antibodies commonly implicated in a DHTR include Kell, Rh, and Duffy system antibodies. The patient's physician should be notified so that additional clinical and laboratory evidence can be evaluated.
