De novodonor-specific antibodies (dnDSAs) that develop after renal transplantation are independent predictors of allograft loss. However, it is unknown ifdnDSA C1q status or titer at the time of first detection can independently predict allograft loss. In a consecutive cohort of 508 renal transplant recipients, 70 developeddnDSAs. Histologic and clinical outcomes were correlated with the C1q assay ordnDSA titer. C1q positivity correlated withdnDSA titer (p < 0.01) and mean fluorescence intensity (p < 0.01) and was more common in class II versus class IdnDSAs (p < 0.01). C1q status correlated with tubulitis (p = 0.02) and C4d status (p = 0.03) in biopsies at the time ofdnDSA development, but not T cell–mediated rejection (TCMR) or antibody-mediated rejection (ABMR).De novoDSA titer correlated with Banff g, i, t, ptc, C4d scores, TCMR (p < 0.01) and ABMR (p < 0.01). Post-dnDSA graft loss was observed more frequently in recipients with C1q-positve dnDSA (p < 0.01) ordnDSA titer ≥ 1:1024 (p ≤ 0.01). However, after adjustment for clinical phenotype and nonadherence in multivariate models, neither C1q status nordnDSA titer were independently associated with allograft loss, questioning the utility of these assays at the time ofdnDSA development.
De novodonor-specific antibody titer and C1q are not independent predictors of allograft survival followingde novodonor-specific antibody development after adjustment for nonadherence and clinical phenotype.