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, Setting, & Participants:We analyzed all adults from 2012-2019 at a quaternary care center in Halifax, NS that underwent diagnostic kidney biopsy to generate an external validation cohort for the "Risk of bleeding complications after kidney biopsy" prediction model (https://perioperativerisk.com/kbrc) which included 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 or surgical intervention/embolization or resulting in death.Analytical Approach: Predicted probabilities from patients in the validation cohort were used to assess 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 1732 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 (Optimismcorrected C-statistic 0.84; (95% CI [0.79 -0.88]; bias-corrected calibration slope 0.82; 95% CI [0.73 -0.88]).