2025 Volume 38 Article ID: oa.24-029
Background and Purpose: In 2014, we developed the cystatin C (cysC)-based eGFR (cysC-eGFR) for Japanese children, using inulin clearance as the gold standard. However, there have been recent reports that the cysC-eGFR overestimates GFR, and we reviewed the validity of the cysC-eGFR at the time of its creation. Methods: The cysC-eGFR was created using company A’s prestandardized cysC values multiplied by a standardization factor, but the cysC values of three other companies at that time existed, and the cysC-eGFRs of four companies were compared by multiplying by each standardization factor. Results: The four equations were not in agreement with each other. The validity of the standardization coefficients of company A was demonstrated when the cysC-eGFR was created. The validity of the currently used eGFR=104.1/cysC-7.80 in Japan was shown to be equivalent to the creatinine-based eGFR in data collected from 2012 to 2016 from the pediatric CKD study group in Japan. Conclusion: The recent GFR overestimation of cysC-eGFR is considered to be issues after 2017, and these need to be discussed in the future.
