Principle:

Unlike acute hemolysis, delayed hemolysis may be insidious and develop over days to weeks.  Likewise severity may vary from asymptomatic but only laboratory-detectable (i.e. delayed serologic reaction) to life-threatening only a few days after transfusion (e.g. an amnestic response to anti-Jka that was undetectable in the compatibility testing several days previously).

Remember that the most severe reactions may occur with weak or negative reactions!!

Policy:

1. In the first encounter of each patient with a positive direct antiglobulin test (DAT), the workup must include an acid-elution.
2. Perform a DAT on patients with dropping hemoglobin levels not attributable to trauma, i.e. an anatomic defect.
3. Obtain the full clinical history, medication history, and transfusion history (including at outside institutions)
   1. Check previous transfusion history.
4. Send the DAT results (poly, IgG, C3d) and acid-elution to the Head, Transfusion Medicine or the Transfusion Medicine Physician covering the service.
   1. If the polyspecific DAT is positive, but only the monospecific C3 is non-negative, check with the Transfusion Medicine physician whether to perform the elution.
   2. He will write an interpretative report/comment appended to the DAT results in Hematos IIG.
5. It is the decision of the Transfusion Medicine Physician preparing the report to decide if the clinician needs to be contacted.

References:

1. Standards for Blood Banks and Transfusion Services, Current Edition, AABB, Bethesda, MD, USA
2. Guidelines to the Preparation, Use, and Quality Assurance of Blood Components, European Committee (Partial Agreement) on Blood Transfusion (CD-P-TS), Current Edition