Updated Pediatric IgAN Prediction Tool for Post-Biopsy Use

By Charlotte Robinson - Last Updated: October 2, 2024

There are existing prediction tools to help determine the risk of disease progression in IgA nephropathy (IgAN). Whereas the adult International IgAN Prediction Tool can be used 1 or 2 years post-biopsy, the pediatric tool can only be used at biopsy. This limits the ability to reevaluate pediatric patient risk after a period of treatment. To address this disparity, Sean J. Barbour, MD, and other researchers attempted to develop an updated pediatric prediction tool for post-biopsy use. Their report appeared in Kidney International.

Advertisement

The original pediatric prediction tool comprises two models with or without ethnicity plus other predictor variables that can be used in children at the time of biopsy. The purpose of this analysis was to move the “baseline” time point to a new landmark 1 year after biopsy. However, due to a limited number of outcome events, it was not possible to refit a new model at this new baseline time point. Instead, Barbour et al updated the adult post-biopsy prediction tool models, intended for use in adults 1 year post-biopsy, for use in children.

The researchers utilized an international, multiethnic cohort of 947 children with biopsy-proven IgAN and frequent follow-up into adulthood to update the adult post-biopsy prediction tool models. The patients they studied were <18 years of age 1 year after kidney biopsy. Those who progressed to end-stage renal disease (ESRD) within the first year, had less than 1 year of follow-up, or did not have at least one estimated glomerular filtration rate (eGFR) measurement before and after the new landmark time of 1 year after biopsy were excluded to ensure adequate baseline and longitudinal follow-up eGFR data.

The primary outcome was a composite of the first incidence of ESRD (eGFR <15 mL/min/1.73 m2, dialysis, or transplantation) or a permanent reduction in eGFR below 30% of the value at the 1-year landmark time. The purpose of the analysis was to predict the risk of the primary outcome in children using models applied at a baseline time point 1 year after biopsy.

The researchers found that neither the adult post-biopsy tool nor the original pediatric prediction tool models have adequate prediction performance to be used without modification in children 1 year after biopsy. The original pediatric prediction tool should be used at the time of biopsy, and the updated pediatric prediction tool should be used to reevaluate risk at 1 or 2 years after biopsy.

Compared with the original pediatric prediction tool, the updated post-biopsy prediction tool had a better model fit, with higher R2D (51%/50% vs 20%), significant increase in 4-year C-statistics (0.83 vs 0.73/0.69), and better 4-year calibration with lower integrated calibration indices (0.74/0.54 vs 2.45/1.01). The results were similar after internal validation and when the models were applied 2 years post-biopsy.

At 1 and 2 years after biopsy, children with higher predicted risk started with a lower eGFR and experienced a more rapid decline over time. Among all risk groups, eGFR had a variable rate of increase until 15-18 years of age; then it decreased linearly, with a more rapid decline in higher-risk groups.

“In conclusion,” the authors summarized, “we used a large, international, multiethnic cohort to generate the pediatric post-biopsy prediction tool that can be used in children with IgAN 1 or 2 years after biopsy to predict the risk of disease progression. This tool allows for reevaluation of individual patient risk after supportive care or immunosuppression treatment implemented in the first 2 years after biopsy.”

Source: Kidney International

 

Advertisement