Flow cytometry crossmatching to investigate kidney-biopsy-proven, antibody-mediated rejection in patients who develop de novo donor-specific antibodies.

Abstract Introduction The appearance of de novo donor-specific anti-human leukocyte antigen antibodies (dnDSAs) after kidney transplantation is independently associated with poor long-term allograft outcomes. The objective of the present study was to evaluate the predictive value of a flow cytometry crossmatching (FC-XM) assay after the appearance of dnDSAs related to antibody-mediated allograft rejection (ABMR) after kidney transplantation. Materials and methods A total of 89 recipients with dnDSAs after transplantation were included. The crossmatching results were compared with the dnDSA profile (the mean fluorescence intensity (MFI), the complement-binding activity, and the IgG subclass profile) and the biopsy's morphological features. Results Of the 89 patients, 59 (66%) were positive in an FC-XM assay, 17 (19%) had complement-binding DSAs, 55 (62%) were positive for IgG1 and/or IgG3 in a solid phase assay, and 45 (51%) had morphological biopsy features linked to ABMR. Conclusion An FC-XM assay was unable to discriminate between cases with or without ABMR on biopsy findings; it had a low positive predictive value ( 3000). In this context, the height of the MFI of the dnDSAs might be enough for a high positive predictive value for ABMR and additional testing for complement binding activity can remain optional.