Direct Antiglobulin = Direct Coombs Test

Detects antibodies bound directly to RBCs. Hemolysis most likely due to something in the transfused blood (not sure why it took 4 weeks when Type 2 HS is supposed to be quicker but w/e).

I think this is delayed hemolytic transfusion reaction (which is why it took 4 weeks and she is not exhibiting signs and symptoms of shock).

From AMBOSS:

Pathomechanism: Occurs in patients who were previously sensitized to specific RBC antigens during transfusions, pregnancy, or transplantations. Re-exposure to the antigens results in a rapid increase in antibodies that bind to donor RBCs and cause extravascular hemolysis

Clinical features: Onset days or weeks after transfusion. Fever, jaundice, anemia, dark urine

Diagnostics: Antibody testing to prevent future reactions

Treatment: No acute therapy required

Regardless of whether it is acute or delayed hemolytic, they are both diagnosed with "direct antiglobulin test"

This is a Delayed Hemolytic Transfusion Reaction (in FA 19 or 20; new topic). Presents after 24 hours but often 1-2 weeks later, may be more. Patient presents with signs of jaundice, low Hb, and high reticulocytes. This occurs when the patient was exposed to a previous minor RBC antigen (NON-ABO). The 1st response is undetected and undocumented. Diagnosis is made with a newly + Direct Coombs test. High unconjugated (NOT conjugated) bilirubin and LDH. Check UW QID 17780.

DHTR(delayed hemolytic transfusion reaction)- mild, hemolytic reaction that occur >24 hours after blood transfusion. Occurs in patients previously exposed to a minor RBC antigens(non-ABO). "+" Combs test.