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Kidney Week

Abstract: TH-PO751

Validation of Different Serum Creatinine-Based Estimating Equations in Pediatric Kidney Transplant Recipients in Comparison with Measured Glomerular Filtration Rate

Session Information

  • Pediatric CKD
    November 07, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
    Abstract Time: 10:00 AM - 12:00 PM

Category: Pediatric Nephrology

  • 1700 Pediatric Nephrology

Authors

  • Dharnidharka, Vikas R., Washington University School of Medicine, St Louis, Missouri, United States
  • Dandamudi, Raja, Washington University School of Medicine, St Louis, Missouri, United States
  • Vyas, Neil, Case Western Reserve University, Forest Hills, New York, United States
  • Hmiel, Stanley P., Washington University School of Medicine, St Louis, Missouri, United States
Background

The evaluation of allograft function is vital in the management of pediatric kidney transplant (pKTx) recipients. Serum creatinine (Scr) is the easiest everyday estimator of glomerular filtration rate (GFR) but both the absolute Scr value and the corresponding estimating equations (eGFR) are prone to considerable error. Measured GFR (mGFR) using plasma clearance of exogenous markers, while very accurate, is laborious as well as expensive, not suitable for everyday use. Prior studies have shown conflicting results regarding which eGFR equations are most accurate in comparison to mGFR. At our center, we have been performing measured GFR at 1 year post-pKTx; repeated every 2 years if mGFR > 40 ml/min/1.73m2, or yearly if mGFR < 40. The aim of this study was to validate the different Scr-based eGFR equations in comparison to mGFR.

Methods

This retrospective study was conducted at St. Louis Children's Hospital from January 2000 to March 2019. We compared 415 mGFR values to 4 different Scr-based pediatric eGFR formulae (original Schwartz formula, modified Schwartz formula, Pottel formula and Modification of Diet in Renal Disease (MDRD) formula) from 125 pKTx recipients. Scr and children’s height was measured on the same day as mGFR. We used Bland-Altman analysis to evaluate the bias between eGFR and mGFR. Higher precision was defined as lower width between the 95% limits of agreement (LOA). Accuracy was defined as percentage of eGFR that are within 30% of mGFR.

Results

The Pottel and modified Schwartz formulae had a high accuracy of 80% each and a low bias of < 5 ml/min/1.73 m2 (Figure). In contrast, the original Schwartz and MDRD formulae displayed a high bias and low precision and accuracy.

Conclusion

Of the Scr-based formulae, height independent Pottel and height dependent modified Schwartz formulae had low bias and high accuracy and either can be used to assess GFR in pKTx recipients. The original Schwartz and MDRD equations should not be used in this population.