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The Creeping Creatinine in a Growing Child With a Kidney Transplant: Distinguishing Progressive Graft Dysfunction
Raja S Dandamudi1, Neil Vyas1, Stanley P Hmiel1
1Division of Pediatric Nephrology, Hypertension and Apheresis, Washington University School of Medicine & St. Louis Children's Hospital, St. Louis, Missouri, USA.
Insights
In pediatric kidney transplant recipients, a stable absolute measured glomerular filtration rate (mGFR) is a better indicator of stable allograft function than BSA-indexed mGFR, especially during growth. This helps differentiate normal growth from potential dysfunction.
Area of Science:
- Nephrology
- Pediatric Transplant Medicine
- Renal Physiology
Background:
- Pediatric kidney transplant recipients often show increasing serum creatinine, termed creeping creatinine.
- Differentiating normal growth-related creatinine changes from allograft dysfunction is challenging.
- Existing metrics like BSA-indexed GFR may not accurately reflect renal function in growing children.
Purpose of the Study:
- To evaluate the reliability of absolute and BSA-indexed measured GFR (mGFR) and estimated GFR (eGFR) for assessing renal function in pediatric kidney transplant recipients.
- To determine if absolute mGFR is a more stable indicator of allograft function than indexed GFR during periods of growth.
Main Methods:
- Retrospective analysis of 115 pediatric kidney transplant recipients with 319 mGFR values.
- Stratification based on height and body surface area (BSA) changes between GFR measurements.
- Analysis of agreement between absolute mGFR and indexed GFR/eGFR using Bland-Altman and Spearman correlation.
Main Results:
- Bias between absolute mGFR and indexed GFR/eGFR increased with greater changes in height and BSA.
- Strong correlation between absolute and indexed GFR was observed only with minimal (<5%) changes in height and BSA.
- Correlation weakened significantly as height and BSA changes increased.
Conclusions:
- BSA-indexed mGFR decreases more in children experiencing significant growth compared to absolute mGFR.
- A stable absolute mGFR is proposed as a more reliable marker for stable allograft function in growing pediatric kidney transplant recipients.
- This finding aids in distinguishing true allograft dysfunction from growth-related physiological changes.
Background:
Pediatric kidney transplant recipients experience creeping creatinine, which is a slow increase in serum creatinine over time. Distinguishing between normal growth-related changes and possible allograft dysfunction becomes challenging when interpreting the increase in serum creatinine. We hypothesized that changes in BSA-indexed measured glomerular filtration rate (mGFR) or creatinine-estimated GFR (eGFR) might not be a true reflection of the renal function post-transplant and that for longitudinal follow-up a stable absolute mGFR is better.
Methods:
In total, 115 pediatric kidney transplant recipients transplanted between 2000 and 2021, with 319 measured GFR values (each subject had at least 2 values) were enrolled in this retrospective study. We analyzed after stratifying based on the height and BSA changes (< 5% change, 5%-14.9% change, and > 15% change in height and BSA) between measured GFR tests. The agreement between absolute mGFR and both BSA-indexed mGFR or eGFR was analyzed by Bland and Altman analysis and nonparametric Spearman's rank order correlation analysis.
Results:
The bias between absolute mGFR and either BSA-indexed mGFR or eGFR increased as the % change in height and the BSA increased. Spearman's rank order correlation showed a strong correlation when the BSA and height changes were < 5% and the correlation weakened as the % changes increased.
Conclusions:
In children who grew more, the BSA-indexed mGFR dropped more than the absolute mGFR. We propose that a stable absolute mGFR can be used to infer stable allograft function in the presence of height growth.
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