Comparison of the association intensity of creatinine and cystatin C with hyperphosphatemia and hyperparathyroidism in patients with chronic kidney disease

Herein, we compared the association intensity of estimated glomerular filtration rate (eGFR) equations using creatinine (Cr) or cystatin C (CysC) with hyperphosphatemia and secondary hyperparathyroidism occurrence, which reflect the physiological changes occurring during chronic kidney disease (CKD) progression. This study included 639 patients treated between January 2019 and February 2022. The patients were divided into low- and high-difference groups based on the median value of the difference between the Cr-based eGFR (eGFR(Cr)) and CysC-based eGFR (eGFR(CysC)). Sociodemographic and laboratory factors underlying a high difference between eGFR(Cr) and eGFR(CysC) were analyzed. The association intensity of eGFR(Cr), eGFR(CysC) and both Cr- and CysC-based eGFR (eGFR(Cr-CysC)) was compared using the area under the receiver operating characteristic curve (AuROC) values for hyperphosphatemia and hyperparathyroidism occurrence in the overall cohort and the low- and high-difference groups. Age > 70 years and CKD grade 3 based on eGFR(Cr) were significant factors affecting the high differences. eGFR(CysC) and eGFR(Cr-CysC) showed higher AuROC values than that of eGFR(Cr), especially in the high-difference group and in patients with CKD grade 3. Our results show that CysC should be evaluated in patients with significant factors, including age > 70 years and CKD grade 3, to accurately assess kidney function to better determine the physiological changes in CKD progression and predict prognosis accurately.