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Kidney Week

Abstract: PO2351

The Creeping Creatinine in a Growing Child with a Kidney Transplant (KT): Using Absolute GFR Values to Separate Age Effects from Progressive Graft Dysfunction

Session Information

Category: Pediatric Nephrology

  • 1700 Pediatric Nephrology

Authors

  • Dandamudi, Raja, Washington University in Saint Louis School of Medicine, Saint Louis, Missouri, United States
  • Hmiel, Stanley P., Washington University in Saint Louis School of Medicine, Saint Louis, Missouri, United States
  • Dharnidharka, Vikas R., Washington University in Saint Louis School of Medicine, Saint Louis, Missouri, United States
Background

In very young KT recipients, the serum creatinine rises and glomerular filtration rate (GFR) decreases over the years. Without a biopsy, judging in a less invasive way whether this decline in GFR is due to linear body growth or progressive chronic allograft dysfunction is difficult. In measured glomerular filtration rate (mGFR) assays, the GFR is reported both as ml/min (ABS-GFR) and ml/min/1.73m2 (body surface area or BSA-GFR).
We hypothesized that children who had rising serum creatinine predominantly due to linear growth would show a minimal change in ABS-GFR, with greater change in BSA-GFR.

Methods

This is retrospective cross-sectional study of 127 children who were aged < 15 years at time of transplant.
We conducted analysis after stratifying basing on the height or BSA changes (< 5% change, 5-14.9% change and >15% change in linear height and BSA) between mGFR tests. Bland–Altman analyses were conducted to determine the agreement between log-ABS-GFR and log-BSA-GFR. We also performed correlation analysis with nonparametric Spearman's rank order correlation coefficient of BSA-GFR and ABS-GFR values.

Results

The bias between ABS-GFR and BSA-GFR increased as the percentage change in height and BSA increases (Figure). Spearman’s rank order correlation demonstrated strong correlation when the BSA and length changes are<5% and the correlation weakened as the % changes increased.

Conclusion

We propose that in longitudinal follow up, it is important to use the ABS-GFR to avoid bias with the indexed GFR due to possible BSA change. A stable absolute GFR can be used to infer stable allograft function.