Kidney Week

Abstract: TH-PO1025

External Validation of the Kidney Failure Risk Equation in Biopsy Proven IgA Nephropathy

Session Information

• Glomerular Diseases: Clinical, Outcomes, Trials - I
  October 25, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1203 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

• Major, Rupert, University Hospitals of Leicester, Leicester, United Kingdom

Rupert Major,

• Jesus Silva, Jorge, University Hospitals of Leicester, Leicester, United Kingdom

Jorge Jesus Silva,

• Medcalf, James F., University Hospitals of Leicester, Leicester, United Kingdom

James F. Medcalf,

• Brunskill, Nigel J., University Hospitals of Leicester, Leicester, United Kingdom

Nigel J. Brunskill,

• Barratt, Jonathan, University Hospitals of Leicester, Leicester, United Kingdom

Jonathan Barratt,

Group or Team Name

• The Mayer Leicester IgA Nephropathy Group

Background

The Kidney Failure Risk Equation (KFRE) has been externally validated in over 30 multi-national multiple aetiology chronic kidney disease (CKD) cohorts. It has high discrimination and good calibration for endstage renal disease (ESRD) events. However, KFRE has not been validated in IgA nephropathy (IgAN). Risk factors for IgAN progression to ESRD may be different to those used in KFRE.

Therefore, our aim was to perform an independent, external validation of the 2 and 5-year 4-variable KFRE in adults with biopsy proven IgAN.

Methods

Using electronic records for the Leicester Renal Network, UK, we assessed model performance of the 2 and 5-year 4-variable KFRE. The C-statistic was used to assess discrimination. Calibration of the KFRE was assessed using the linear predictor’s calibration slope and observed versus predicted event rates plots with risk categories of 0 to <5%, ≥5% to <25% and ≥25%.

Results

The cohort consisted of 353 individuals with biopsy proven IgAN, of whom 166 had CKD stages 3-5 at their biopsy date. In CKD stages 3-5, mean age was 49.2 (SD 14.4) years, 30.1% were female, mean EPI eGFR was 37.6 l/min/1.73m² (SD 13.5) and median ACR was 52.2 (IQR 2.2 to 124.6) mg/mmol. 59 (35.5%) ESRD events occurred over median follow-up of 3.6 (IQR 1.5 to 7.7) years. For eGFR and ACR nearest to the date of biopsy, discrimination by KFRE was good (Harrell’s C-statistic 0.71, 95% CI 0.62 to 0.81), although possibly inferior to the published model (Harrell’s C-statistic 0.90, 95% CI 0.87 to 0.93). The linear predictor for calibration was 0.29 (95% CI 0.14 to 0.44). Calibration plots suggested that risk was over estimated at 2 and 5 years for low (<5%) KFRE predicted risk groups. For higher risk groups, the model was well calibrated. Results were similar when earliest available, instead of biopsy, eGFR and ACR were used in KFRE.

Conclusion

In an independent, external validation of KFRE in biopsy proven IgAN, discrimination was good but calibration was poor in lower predicted risk individuals. For patients with biopsy proven IgAN, the KFRE may need model adjustment, particularly for lower predicted risk individuals. Adjustments may be required to existing variables and/or inclusion of other variables, such as Oxford Classification histology findings, before KFRE can be used for prognostic purposes in IgAN.