Although the current Banff criteria requires positive C4d peritubular capillary (PTC) staining for a definitive diagnosis of ABMR, it has become clear that C4d is neither completely specific nor sufficiently sensitive for diagnosis of ABMR. We aim to investigate clinical and pathological features of C4d positive and negative ABMR patients, and the influence of C4d positivity for prognosis. From 2005 to 2011, 626 kidney transplantations were performed at our institution. We excluded 174 ABO-incompatible transplants and analyzed clinical and pathological data from remaining 452 transplants. A total of 1027 allgraft biopsies were performed. Among these, 217 biopsies (21%) showed microvascular inflammation (peritubular capillaritis and glomerulitis, MVI). C4d deposition with MVI were detected in 62 samples (29%). We hypothesized diagnostic criteria of ABMR as presence of donor-specific antibodies and morphological features of ABMR. C4d positivity was not included in our criteria. Thirty-nine patients (92biopsies) were diagnosed as acute ABMR. Of these, 39 biopsies (42%) were C4d negative. We divided biopsies into 2 groups. Group A (N=53): samples with C4d positive and MVI, and presence of DSA (conventional ABMR). Group B(N=39): samples with C4d negative and MVI and presence of DSA (C4d negative ABMR). Both ptc and g scores were higher in group A than in group B (1.9 ± 0.40 and 1.5 ± 0.17, respectively). We compared both group A and group B with control group (N=45). Glomerular filtration rate were similar in group A and group B (40 ± 9.8 ml/min and 38 ± 11 ml/min, respectively), but better in control group (58 ± 19 ml/min). Group A and group B patients progressed to chronic ABMR similarly, but patients in control group less progressed to chronic ABMR. Two patients (1 patient in group A and 1 in group B, respectively), lost their graft function, on the other hand, no patient in the control group did. We concluded that C4d negative ABMR was often observed, resembles C4d positive ABMR in clinical features, also progressed to chronic ABMR and had a poor prognosis similarly as C4d positive ABMR, thus C4d positivity should not be included in criteria of ABMR.
To cite this abstract in AMA style:Sai K, Omoto K, Tanabe T, Shirakawa H, Setoguchi M, Shimizu T, Honda K, Ishida H, Tanabe K. Microvascular Inflammation as a Core Element of Diagnostic Criteria of Antibody-Mediated Rejection (ABMR): C4d Positivity Is Not Reliable Element in Diagnosis of ABMR [abstract]. Am J Transplant. 2013; 13 (suppl 5). https://atcmeetingabstracts.com/abstract/microvascular-inflammation-as-a-core-element-of-diagnostic-criteria-of-antibody-mediated-rejection-abmr-c4d-positivity-is-not-reliable-element-in-diagnosis-of-abmr/. Accessed May 6, 2021.
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