Banff-based histologic chronicity index is associated with graft failure but has poor interobserver reproducibility

Area of Science:

• Nephrology
• Transplantation Immunology
• Pathology

Background:

• Antibody-mediated rejection (AMR) is a primary cause of chronic kidney allograft damage and failure.
• The Banff classification for AMR diagnosis is complex.
• A simplified Banff-based histologic chronicity index (CI) was proposed but lacks external validation.

Purpose of the Study:

• To assess the interobserver reproducibility of the proposed CI and its components in kidney allograft biopsies.
• To evaluate the association between CI and kidney allograft failure.
• To determine the reliability of proposed CI cut-off values for predicting allograft outcomes.

Main Methods:

• Analysis of 71 kidney allograft biopsies diagnosed with AMR.
• Assessment of interobserver agreement for CI and its components (cg, cv, ct, ci).
• Cox regression and Kaplan-Meier analysis to evaluate CI's association with allograft failure and test cut-off values.

Main Results:

• The CI was associated with allograft failure, but its assessment showed significant variability among pathologists.
• Complete agreement on the proposed CI cut-off (<4 vs. ≥4) was achieved in only 69.0% of biopsies.
• The cg score, a key component of CI, exhibited the lowest interobserver agreement (kappa = 0.281), and the cut-off did not reliably stratify failure risk.

Conclusions:

• The proposed CI has limitations due to poor interobserver reproducibility, impacting its utility as a prognostic tool for AMR.
• Clinicians should exercise caution when interpreting CI and may need to establish personalized cut-off values.
• Further work is required to improve interobserver reproducibility before widespread adoption of CI for AMR management.