Panagglutination in a Patient With Life-Threatening Anemia
A 62-year-old woman is admitted with melena and fatigue. Her hemoglobin is 6.4 g/dL, platelets 220 × 10^9/L, INR 1.1, and creatinine is normal. She is tachycardic at 112/min but normotensive. The blood bank receives a request for 2 units of RBCs. Her antibody screen shows 3+ agglutination with all three screen cells at AHG, and the DAT is positive (IgG 2+, C3 1+). She was transfused 5 years ago and has had two pregnancies. She takes no medications known to cause hemolysis. The eluate is also panreactive. The technologist considers issuing least-incompatible units immediately because of the hemoglobin.
1. What is the differential diagnosis for these serologic findings, and what additional testing should be performed before selecting RBCs?
Read the worked answer
The leading diagnosis is a warm autoantibody, but the workup must exclude a masked alloantibody. Because the last transfusion was 5 years ago, autoadsorption is valid; alloadsorption with phenotyped reagent cells is needed if autoadsorption is invalid (for example, transfusion within the previous 3 months). Perform adsorption, test the adsorbed serum against a panel, and review the history for drugs and prior antibodies. Do not delay transfusion in a symptomatic patient with Hb 6.4 g/dL; communicate that crossmatch-incompatible units may be needed while testing proceeds.
2. If autoadsorption reveals anti-E plus a warm autoantibody, how should units be selected and what monitoring is needed?
Read the worked answer
Select E-negative RBC units. Crossmatch by AHG; use compatible E-negative units if found. If all units remain incompatible because of the autoantibody, use least-incompatible E-negative units and monitor for hemolysis with Hb, bilirubin, LDH, haptoglobin, and urine studies. Do not withhold transfusion if the patient is unstable. Consider hematology consultation for corticosteroids and provide the patient with antibody documentation.
3. How would the approach change if the patient had been transfused 2 weeks ago?
Read the worked answer
Autoadsorption would be contraindicated because donor cells in the circulation can adsorb alloantibody and produce a false-negative result. Use alloadsorption with phenotyped donor cells or RBC genotyping to identify underlying alloantibodies. If the patient is unstable, issue least-incompatible units while the workup continues, and document the limitation.