Kidney Week

Abstract: PO1974

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

Session Information

• Pediatric Nephrology: AKI, Dialysis, Transplant, CKD, and Nephrotic Syndrome
  November 04, 2021 | Location: On-Demand, Virtual Only
  Abstract Time: 10:00 AM - 12:00 PM

Category: Pediatric Nephrology

• 1700 Pediatric Nephrology

Authors

• Bokenkamp, Arend, Amsterdam UMC Locatie VUmc, Amsterdam, Noord-Holland, Netherlands

Arend Bokenkamp, MD, PhD, FASN

• Oostdam, Tobias, Amsterdam UMC Locatie VUmc, Amsterdam, Noord-Holland, Netherlands

Tobias Oostdam,

• Björk, Jonas, Lunds Universitet, Lund, Sweden

Jonas Björk,

• Nyman, Ulf, Skanes universitetssjukhus Malmo, Malmo, Skåne, Sweden

Ulf Nyman,

• Goffin, Karolien, Katholieke Universiteit Leuven Universitaire Ziekenhuizen Leuven, Leuven, Flanders, Belgium

Karolien Goffin,

• Åsling Monemi, Kajsa, Karolinska Universitetssjukhuset, Stockholm, Sweden

Kajsa Åsling Monemi,

• Hansson, Magnus Daniel, Karolinska Universitetssjukhuset, Stockholm, Sweden

Magnus Daniel Hansson,

• Berg, Ulla B., Karolinska Universitetssjukhuset, Stockholm, Sweden

Ulla B. Berg,

• Littmann, Karin, Karolinska Universitetssjukhuset, Stockholm, Sweden

Karin Littmann,

• Grubb, Anders O., Lunds Universitet, Lund, Sweden

Anders O. Grubb,

• Pottel, Hans, Katholieke Universiteit Leuven Universitaire Ziekenhuizen Leuven, Leuven, Flanders, Belgium

Hans Pottel,

• Den bakker, Emil, Amsterdam UMC Locatie VUmc, Amsterdam, Noord-Holland, Netherlands

Emil Den bakker,

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 (FAS_α) 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 FAS_0.3 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 FAS_0.3 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.