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Abstract: PO1974

Diagnosis-Specific Combination of Cystatin C- and Creatinine-Based eGFR

Session Information

Category: Pediatric Nephrology

  • 1700 Pediatric Nephrology

Authors

  • Bokenkamp, Arend, Amsterdam UMC Locatie VUmc, Amsterdam, Noord-Holland, Netherlands
  • Oostdam, Tobias, Amsterdam UMC Locatie VUmc, Amsterdam, Noord-Holland, Netherlands
  • Björk, Jonas, Lunds Universitet, Lund, Sweden
  • Nyman, Ulf, Skanes universitetssjukhus Malmo, Malmo, Skåne, Sweden
  • Goffin, Karolien, Katholieke Universiteit Leuven Universitaire Ziekenhuizen Leuven, Leuven, Flanders, Belgium
  • Åsling Monemi, Kajsa, Karolinska Universitetssjukhuset, Stockholm, Sweden
  • Hansson, Magnus Daniel, Karolinska Universitetssjukhuset, Stockholm, Sweden
  • Berg, Ulla B., Karolinska Universitetssjukhuset, Stockholm, Sweden
  • Littmann, Karin, Karolinska Universitetssjukhuset, Stockholm, Sweden
  • Grubb, Anders O., Lunds Universitet, Lund, Sweden
  • Pottel, Hans, Katholieke Universiteit Leuven Universitaire Ziekenhuizen Leuven, Leuven, Flanders, Belgium
  • Den bakker, Emil, Amsterdam UMC Locatie VUmc, Amsterdam, Noord-Holland, Netherlands
Background

The arithmetic mean of a creatinine- and a cystatin C-based GFR estimation (eGFR) has higher accuracy than either of the two. Smaller studies indicate that the relative contribution of the creatinine- and the cystatin C-based equation should be adapted based on underlying diagnosis.

Methods

Retrospective analysis of 1712 plasma clearance GFR measurements from four pediatric nephrology centers. eGFR was calculated using the height-based Full Age Spectrum equation using creatinine (FAS-creat) and the FAS-cys equation for cystatin C. α describes the contribution of FAS-creat, (1-α) the contribution of FAS-cys. 2/3 of the cohort (mean age 11.8 years, mGFR 93.8 ml/min/1.73m2) was used to determine the α-values yielding the highest P30 accuracy globally (FASα) and in diagnosis subgroups. These α-values were validated in the remaining 1/3 of the cohort assessing accuracy, bias and precision.

Results

Globally, the optimal α-value was 0.3 [95% CI 0.2 – 0.4, Figure]. Lower α-values were determined for spina bifida (0), glomerulonephritis (0.2), and liver disease (0.25), while CAKUT, kidney transplantation and tubulointerstitial disease had α-values between 0.35 and 0.55.
Accuracy of FAS0.3 in the validation cohort was 90.2%, which was significantly higher than accuracy of the arithmetic mean (87.4%, p<0.05). Using the diagnosis-specific α-values rather than FAS0.3 improved bias (+2.5 vs +1.3 ml/min/1.73m2, p < 0.01) and precision (14.1 vs 13.8 ml/min/1.73m2, p < 0.05), while accuracy was unchanged. Only in children with spina bifida, a clinically relevant improvement was observed when using the diagnosis-specific α-value.

Conclusion

For calculation of the weighted mean, a fixed mix of 30% FAS-creat and 70% FAS-cys is optimal and yields very high accuracy overall. A disease-specific adaption (i.e. 100% cystatin C eGFR) is clinically relevant only for patients with spina bifida.