External Validation and Recalibration of a Risk Calculator for Major Bleeding After Diagnostic Kidney Biopsy.

Rationale & Objective: Bleeding is a serious complication of diagnostic kidney biopsy. A risk calculator for major bleeding associated with kidney biopsy exists, but its performance has not been tested externally. Study Design: Retrospective cohort study. Setting & Participants: We collected data from all adults who underwent diagnostic kidney biopsy from 2012 to 2019 at a quaternary care center in Halifax, NS to generate an external validation cohort for the "Risk of bleeding complications after kidney biopsy" prediction model (https://perioperativerisk.com/kbrc), which includes the predictors of age, weight, height, platelet count, hemoglobin, kidney size, and native versus transplant graft kidney. Outcomes: Major bleeding was defined as the need for blood transfusion, surgical intervention/embolization, or death. Analytical Approach: Predicted probabilities from patients in the validation cohort were used to assess the model, which was then re-examined using a larger combined cohort of patients from both model derivation and validation datasets. Results: External validation was performed using 715 patients in an external validation cohort from Halifax, NS. Major bleeding occurred in 48 of 1,732 patients in the combined cohort, with a total major bleeding risk of 2.7%. The model demonstrated good overall discrimination performance in the validation cohort (C-statistic, 0.78; 95% CI, 0.69-0.85) and was well calibrated (calibration slope, 0.72; 95% CI, 0.41-1.02). Recalibration improved performance in the combined cohort; model performance improved with the combined dataset (optimism-corrected C-statistic, 0.84 [95% CI, 0.79-0.88]; bias-corrected calibration slope, 0.82 [95% CI, 0.73-0.88]). Limitations: Although model extension was performed with a relatively large patient cohort, the precision of performance remained limited by the small number of major bleeding events. Conclusions: In this study, a risk calculator for predicting major bleeding complications from kidney biopsy demonstrated good model performance in an external validation that improved with recalibration in a combined cohort. This model can be used to individualize patient risk assessment for kidney biopsy-related major bleeding events, facilitating preprocedural optimization and more efficient allocation of postprocedural monitoring.