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Abstract: SA-PO953

Validation of the International Immunoglobulin A (IgA) Risk Prediction Tool in American Indians and Hispanics

Session Information

Category: Glomerular Diseases

  • 1402 Glomerular Diseases: Clinical, Outcomes, and Trials

Authors

  • Shaffi, Saeed Kamran, Raymond G. Murphy VA Medical Center, Albuquerque, New Mexico, United States
  • Fischer, Edgar G., University of New Mexico School of Medicine, Albuquerque, New Mexico, United States
  • Wagner, Brent, Raymond G. Murphy VA Medical Center, Albuquerque, New Mexico, United States
Background

The International IgA risk prediction equation performance has not been studied in the Hispanic and American Indian population. Studies have reported a higher frequency of IgAN in American Indians. Therefore, we conducted this single-center study based in New Mexico to assess the performance of the International IgA risk prediction tool without race/ethnicity.

Methods

We searched the University of New Mexico kidney biopsy registry - a repository of kidney biopsies from 2002 -2016 - for instances of IgA nephropathy. We calculated the 5-year risk of developing kidney failure and assessed the equation performance using the metrics of calibration, discrimination, and overall prediction error in patients with primary IgA nephropathy on whom the predictions variables were available.

Results

Thirty-four patients were included, most of whom identified as of Hispanic race/ethnicity (44.1%), or as American Indians (26.5%). At biopsy, the median (IQR) age, serum creatinine, and spot urine protein to creatinine ratio were 38 years (27-45), 2.15 mg/dl (1.51-3.04), and 2.7 g/g (1.5-5.8), respectively. The equation identified patients at high risk of developing kidney failure early with a concordance statistic of 0.79 (95% CI 0.68 – 0.89). The agreement between observed and predicted outcomes at 5 years was marginal, with over-estimation of risk for patients with low observed risk and vice versa. Overall prediction error was suboptimal in this cohort [index of prediction accuracy 0.34 (0.03 -0.51)].

Conclusion

The International IgAN risk prediction equation without race accurately identified patients at elevated risk of developing kidney failure. At 5 years, the agreement between the observed and predicted outcomes was sub-optimal, possibly due to advanced kidney disease in this cohort. A diverse development population may improve the risk prediction.

Performance measures of the International IgAN Risk Prediction Tool without race in the study cohort
MetricValue
Discrimination
C-Statistics at 5 years0.79 (0.64 – 0.79)
Area Under the Curve at 5 years0.79 (0.68 – 0.89)
Calibration
Observed/Estimated Risk at 5 years (O/E)0.88 (0.51 – 1.25)
Calibration Intercept0.10 (-0.37 – 0.58)
Calibration Slope3.03 (0.43 – 5.64)
Overall Prediction Error
Index of Prediction Accuracy (IPA)0.33 (0.02 – 0.50)