Incidence and risk factors of passenger lymphocyte syndrome after <scp>ABO</scp> minor‐incompatible lung transplantation

Abstract Objective To investigate the incidence and risk factors of Passenger Lymphocyte Syndrome (PLS) following ABO minor‐incompatible lung transplantation. Methods A retrospective analysis was performed on 211 lung transplantations conducted between January 2022 and July 2025, including 58 cases involving ABO minor‐incompatibility. The diagnosis of PLS was established based on evidence of haemolysis, a positive direct antiglobulin test (DAT), and confirmation of donor‐derived antibodies. Clinical characteristics and outcomes were compared between the PLS and non‐PLS groups using statistical analyses. Results The overall incidence of PLS was 3.32% (7/211), with a markedly higher rate of 12.07% (7/58) observed among ABO minor‐incompatible transplants. Of the seven PLS cases, six occurred in O‐to‐non‐O donor–recipient pairs. Risk factor analysis revealed that female sex ( p &lt; 0.001), bilateral lung transplantation ( p = 0.027), and preoperative anaemia ( p &lt; 0.001) were significantly associated with the development of PLS. Furthermore, patients with PLS experienced several adverse postoperative outcomes, including lower nadir haemoglobin levels (43.50 g/L vs. 77.00 g/L in controls, p = 0.001) and platelet counts (29.00 × 10 9 /L vs. 101.00 × 10 9 /L, p = 0.001), substantially higher median red blood cell transfusion requirements (23.25 units vs. 0.00 units in controls, p &lt; 0.001), and prolonged median hospital stays (75.50 days vs. 32.00 days, p = 0.002). Conclusion PLS occurs at a relatively high frequency following ABO minor‐incompatible lung transplantation. It is associated with risk factors such as female sex, bilateral lung transplantation, and preoperative anaemia, and contributes to more pronounced postoperative declines in haemoglobin and platelet levels, increased transfusion requirements, and extended hospitalisation.