Molecular Diagnostics Supporting a ≥35% Diffuse Peritubular Capillaritis Extent Threshold for Diagnosis of AMR—A Retrospective Dual Center Study

International Journal of Molecular Sciences, vol. 26, pp. 10945

Abstract

Peritubular capillaritis (ptc) is a hallmark lesion of antibody-mediated rejection (AMR), but the grading of its extent is historically based on arbitrary defined cut-offs. Molecular AMR diagnosis via intragraft gene expression measurements may provide evidence to challenge established ptc categories. We retrospectively included 38 renal allograft biopsies from clinical routine, performed because of suspicion of AMR. Biopsies were re-assessed by an experienced nephropathologist and intragraft gene expression was measured using the NanoString nCounter® platform. Ptc categories were correlated with AMR gene expression to identify a ptc extent cut-off with optimal prediction of molecular diagnosis of AMR [gene expression levels above first quartile (AMRQ>1)]. Finally, an independent validation cohort (n = 25, Erasmus MC, Rotterdam, The Netherlands) was included to reproduce the results. Re-assessment of biopsies revealed AMR in 26/68.4%, mixed rejection in 5/13.2%, and T-cell-mediated rejection in 3/7.9%. Biopsies with diffuse ptc had significantly higher AMR gene expression compared to biopsies with focal ptc and biopsies with no ptc (64.0/53.3–84.0 vs. 31.5/27.0–49.5, p = 0.023 and 27.0/14.3–31.8, p = 0.003, median/IQR). Sensitivity analysis revealed that a ≥35% ptc cut-off resulted in higher AUCs for predicting AMRQ>1 compared to ptc50% (AUC 0.78, 95% CI: 0.63–0.93, p = 0.009 versus AUC: 0.74, CI: 0.56–0.90, p = 0.03). In the validation cohort, only the ptc35–, but not the ptc50%, cut-off significantly predicted AMRQ>1 (AUC 0.75, 95% CI: 0.54–0.96 p = 0.04 vs. AUC 0.69, CI: 0.46–0.93, p = 0.13). Using intragraft gene expression measurement, we identified a new ptc extent threshold with better prediction of molecular AMR. The newly proposed cut-off of ≥35% could potentially improve diagnostic evaluation and prognostication in cases with suspected or diagnosed AMR.

Authors 8

1. Michael Eder

   Medical University of Vienna

   Affiliation as printed

   Division of Nephrology and Dialysis, Department of Internal Medicine III, Medical University of Vienna, Währinger Gürtel 18–20, 1090 Vienna, Austria

2. Marian C. Clahsen‐van Groningen Aachen Department of Nephrology

   Erasmus MC · Universitätsklinikum Aachen · Erasmus MC Transplant Institute · RWTH Aachen University

   Affiliation as printed

   Department of Pathology and Clinical Bioinformatics, Erasmus MC Transplant Institute, 3015 GD Rotterdam, The Netherlands

   Laboratory for Pathology (PAL), 3318 AL Dordrecht, The Netherlands

   University Hospital RWTH Aachen, Department of Nephrology, 52074 Aachen, Germany

3. Michael Mengel

   University of Alberta

   Affiliation as printed

   Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB T6G 2R3, Canada

4. Haris Omić

   Medical University of Vienna

   Affiliation as printed

   Division of Nephrology and Dialysis, Department of Internal Medicine III, Medical University of Vienna, Währinger Gürtel 18–20, 1090 Vienna, Austria

5. Daniel Cejka

   Krankenhaus der Elisabethinen

   Affiliation as printed

   Department of Medicine III, Nephrology, Hypertension, Transplantation and Rheumatology, Ordensklinikum Linz-Elisabethinen, 4010 Linz, Austria

6. Benjamin Adam

   University of Alberta

   Affiliation as printed

   Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB T6G 2R3, Canada

7. Nicolas Kozakowski

   Medical University of Vienna

   Affiliation as printed

   Department of Pathology, Medical University of Vienna, 1090 Vienna, Austria

8. Željko Kikić corresponding

   Medical University of Vienna

   Affiliation as printed

   Department of Urology, Medical University of Vienna, 1090 Vienna, Austria

   Division of Nephrology and Dialysis, Department of Internal Medicine III, Medical University of Vienna, Währinger Gürtel 18–20, 1090 Vienna, Austria