A 10-year-old patient with aplastic anemia, who is blood type B negative, is receiving a red blood cell transfusion. About 10 minutes after the transfusion starts, the patient develops anxiety and lower back pain. The transfusion continues for another 5 minutes until it is stopped when he develops a temperature of 40 °C with chills and rigors. A transfusion reaction work-up is most likely to reveal what findings?
Correct Answer: D
Rationale: The correct answer is D because in this scenario, the patient is experiencing symptoms of a transfusion reaction, likely a hemolytic transfusion reaction due to ABO incompatibility. The presence of a positive Direct Antiglobulin Test (DAT) for C3 indicates complement activation, supporting the diagnosis.
Choice A (Spherocytes on peripheral blood smear) is incorrect as spherocytes are seen in autoimmune hemolytic anemia, not typically in transfusion reactions.
Choice B (Gram-negative Bacillus on gram stain of remaining RBC unit) is unlikely as the symptoms are more indicative of a hemolytic reaction rather than an infection.
Choice C (Chest x-ray with bilateral pulmonary infiltrates) is suggestive of transfusion-related acute lung injury (TRALI), but the symptoms described in the question (fever, chills, rigors) are more indicative of a hemolytic reaction rather than TRALI.