Panreactive Antibody Screen Before Elective Orthopedic Surgery
Ms. R, 62, is scheduled for elective revision of an infected total hip arthroplasty. Hemoglobin is 7.9 g/dL and platelets are 210 × 10⁹/L. Type and screen: A positive; the antibody screen is 3+ in all three screening cells and the autocontrol is also 3+; the identification panel shows 3+ reactivity with every cell. The direct antiglobulin test is positive for IgG (2+) and negative for C3. She received two units of red cells three years ago after a postpartum hemorrhage and has no history of a delayed transfusion reaction. The surgeon wants two units of packed red cells available for the morning case. The operating room does not stock O-negative, the blood bank's reference laboratory has a 24-hour turnaround for complex serology, and no autologous units are available. The technologist on duty asks whether the case should be postponed until a full workup is complete.
1. What is the most likely explanation for this serologic picture, and what testing must be completed before units are assigned?
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The pattern - panagglutination in all phases, a positive autocontrol, and an IgG-only DAT - is a warm autoantibody. However, roughly 30% of patients with warm autoantibodies also carry an underlying alloantibody that the panagglutinin masks, so the workup cannot stop at that conclusion.
Steps: (1) Phenotype or, preferably, genotype the patient for Rh (C/c, E/e), Kell, Kidd, Duffy and MNS. Genotyping is more reliable when the autoantibody and any prior transfusion confound phenotyping. (2) Perform adsorptions and test the adsorbed plasma against a full panel. Autoadsorption is valid here because she has not been transfused within three months; allogeneic adsorption with three to four phenotyped cells is the alternative. (3) An eluate can confirm the autoantibody but does not by itself exclude an underlying alloantibody. If the adsorbed plasma is negative against the panel, no alloantibody is demonstrable, and units matched for Rh and Kell are appropriate. If the panel cannot be resolved, refer to the reference laboratory rather than issuing unmatched units blindly.
2. How should blood be provided for the morning case given these constraints?
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Do not cancel for lack of 'compatible' units. In warm autoimmune hemolytic anemia with no demonstrable alloantibody, the standard is to transfuse the least incompatible units with antigen matching for Rh and Kell (extended to other systems if genotype suggests prior alloimmunization). The crossmatch will remain incompatible, and that is expected.
Practical steps: reserve two units, arrange them for the morning, and attach a comment to the units and the patient record explaining the serology. The pathologist should speak directly to the surgeon and the anesthesiologist so nobody interprets the incompatible crossmatch as a new emergency. At 7.9 g/dL for an elective revision, also ask whether transfusion is needed at all and whether preoperative optimization is possible - the trigger should be clinical, not a number. If the patient deteriorates before the workup is complete, issue O-negative or type-specific units immediately; a serologic workup never justifies delaying emergency hemorrhage control.
3. How would the plan change if she had received a transfusion six days ago?
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Autoadsorption becomes invalid. After recent transfusion the patient's plasma contains donor red cells as well as her own; an autoadsorbent prepared from her post-transfusion sample would remove alloantibody bound to donor cells along with the autoantibody, producing a false-negative result.
The approach shifts to allogeneic adsorption using four to six thoroughly phenotyped reagent cells, testing the adsorbed plasma against the panel. Phenotyping is also unreliable because the circulating red cells are a mixture of donor and recipient, so molecular genotyping is needed to establish her true antigen profile. In addition, recent transfusion raises the possibility of a delayed hemolytic transfusion reaction, so review the DAT, eluate, hemoglobin trend, bilirubin and LDH, and obtain a post-transfusion sample rather than relying on the admission specimen.