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Transplant Direct. 2019 Jun 27;5(7):e470. doi: 10.1097/TXD.0000000000000915. eCollection 2019 Jul.

Complement Markers in Blood and Urine: No Diagnostic Value in Late Silent Antibody-Mediated Rejection.

Author information

1
IIIrd Department of Internal Medicine and MTA-SE Research Group of Immunology and Hematology, Research Laboratory, Hungarian Academy of Sciences and Semmelweis University, Budapest, Hungary.
2
Department of Pediatrics and Adolescent Medicine, Medical University of Vienna, Vienna, Austria.
3
Division of Nephrology and Dialysis, Department of Medicine III, Medical University of Vienna, Vienna, Austria.
4
Department of Clinical Pathology, Medical University of Vienna, Vienna, Austria.
5
Alberta Transplant Applied Genomics Centre, ATAGC, University of Alberta, Edmonton, AB, Canada.

Abstract

Background:

Antibody-mediated rejection (AMR) is a major cause of kidney allograft failure. Its molecular mechanisms are multifaceted and may include a role of complement activation via the classical pathway. Here, we investigated whether noninvasive complement monitoring adds predictive power to the diagnosis of AMR in the setting of donor-specific antibody (DSA) positivity.

Methods:

In this cross-sectional study, 741 kidney transplant recipients with stable graft function ≥180 days posttransplantation were screened for the presence of human leukocyte antigen (HLA) alloantibodies. Eighty-three of 111 DSA-positive recipients underwent protocol biopsies and were tested for blood and urinary levels of complement proteins (C1q, C4, C3) and activation products (C4d, C3a, C5a, C5b-9).

Results:

Forty-seven recipients were diagnosed with AMR, and 21 were C4d-positive. While biopsy-confirmed AMR (and C4d) associated with DSA-binding strength (IgG mean fluorescence intensity of the immunodominant DSA versus AMR; area under the receiver operating characteristic curve: 0.76), tested complement markers did not have any predictive value for rejection (area under the receiver operating characteristic curve: 0.49-0.56). There were, however, tight correlations between complement activation products in urine and protein/creatinine ratio (ρ = 0.44-0.64; P < 0.001). Analysis of death-censored graft survival over a median of 60 months revealed no independent associations with levels of complement markers in blood or urine.

Conclusions:

Complement patterns in blood and urine failed to identify AMR in late biopsies and may have no relevant diagnostic value in this particular context.

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