Background: In a previous study we searched the association between the flow cytometry cross-match assay (FXM) result and the results obtained in the analysis of the C1q-SAB assay in a group of kidney transplant candidates with DSA against their potential living donors and a negative CDC cross-match in all cases. We found that for FXM prediction: the combination of DSA and C1q+Ab was the most specific (95.8%, 85-100), and the combination of DSA-MFI > 2,300 and C1q+Ab, the most sensitive (92%, 79.1-100). In this study we analyze the performance of the C3d assay as an alternative to C1q assay in a new group of patients with a similar clinical profile. Aim: To establish the DSA MFI level with the best sensitivity and specificity in predicting FXM and compare it with the C3d assay's predictive capacity in patients with DSA(s) and AHG-CDC CxM negative. Methods: We used cryopreserved (-70C) sera from potential renal transplant recipients (PRT), containing DSA(s) against their respective donors- all had negative AHG-CDC CxM and either positive or negative FXM. Results: Of the 92 FXM performed, 27 were positive. The median MFI of the immunodominant DSA was 1684 (IQR 1038 – 3882). 31 patients (33.7%) have at least one C3d+ HLAab, and only 10 of them could be assigned as donor specific. The best predictive cutoff value of immunodominant DSA MFI was 2000. The diagnostic performance was summarized in table 1.

Conclusions: The conjunction of the findings of low MFI DSA (< 2000) and the absence HLAab C3d+, have a high negative predictive value to FXM.

CITATION INFORMATION: Contreras A, Casillas A, Castelan N, Gonzalez-Tableros N, Lopez M, Arvizu A, De Santiago A, Alberu J, Arreola-Guerra J. C3d Assay Result in Potential Transplant Recipients with HLA-DSA, AHG-CDC CxM Negative and FxM Positive or Negative with Their Potential Donors. Am J Transplant. 2017;17 (suppl 3).

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