ObjectiveThe Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) reported two equations in 2012: one based on cystatin C concentration (CKD-EPI2012cys) and the other using both serum creatinine and cystatin C concentrations (CKD-EPI2012Scr-cys). We compared the adaptability of new formulae with other four equations.MethodsParticipants (n = 788; median age, 54 [range, 19–94] years) were recruited from the First Affiliated Hospital of Nanjing Medical University. The reference glomerular filtration rate (rGFR) was measured by a 99mTc-DTPA renal dynamic imaging method, and the estimated glomerular filtration rate (eGFR) was calculated separately by the Chinese adapted Modification of Diet in Renal Disease equation (C-MDRD), MacIsaac, Ma, serum creatinine-based CKD-EPI equation (CKD-EPI2009Scr), CKD-EPI2012cys and CKD-EPI2012Scr-cys equations. We compared the performance of six equations with rGFR.ResultsMedian rGFR was 76.35 (interquartile range, 59.03–92.50) mL/min/1.73 m2. Compared with CKD-EPI2009Scr, CKD-EPI2012Scr-cys formula had better diagnostic value with larger area under the receiver operating characteristic curve (ROCAUC, 0.879, p = 0.006), especially in young participants (ROCAUC, 0.883, p = 0.005). CKD-EPI2012cys equation did not perform better than other available equations. Accuracy (the proportion of eGFR within 30% of rGFR [P30]) of the CKD-EPI2012Scr-cys equation (77.03%) was inferior only to MacIsaac equation (80.2%) in the entire participants, but performed best in young participants with normal or mildly-injured GFR. Neither of the two new CKD-EPI equations achieved any ideal P30 in the elderly participants with moderately-severely injured GFR. Linear regression analysis demonstrated a consistent result. In this study, CKD-EPI2012Scr-cys had a relatively better diagnosis consistency of GFR stage between the eGFR and rGFR in the whole cohort.ConclusionCKD-EPI2012Scr-cys appeared less biased and more accurate in overall participants. Neither of the new CKD-EPI equations achieved ideal accuracy in senior participants with moderately-severely injured GFR. A large-scale study with more subjects and cooperating centers to develop new formulae for the elderly is assumed to be necessary.

ObjectiveThe present study aimed to establish reference intervals for serum cystatin C (Scys-C) stratified by stages of chronic kidney disease, explore factors influencing Scys-C and compare the performance of Scys-C with serum creatinine (Scr) in the young and elderly.MethodsA total of 800 participants, 516 young (<60 years) and 284 old (≥60 years) subjects were included in this study. Scys-C and Scr were assayed by the partical-enhanced immunoturbidimetry method and enzymatic method respectively. 95% reference interval was adopted to evaluate reference intervals. Influencing factors were characterized by multivariate linear regression analysis. Relationship between reference glomerular filtration rate (rGFR) and Scys-C or Scr was determined by correlation coefficient.ResultsReference intervals for Scys-C were calculated to be 0.71–1.38 mg/L, 0.83–1.67 mg/L, 1.02–2.61 mg/L, 1.32–4.48 mg/L, 1.95–6.11 mg/L in the aged in CKD G1, G2, G3a, G3b and G4-5 stages, respectively. Body mass index(BMI), nephritis, kidney neoplasm and hypertension were demonstrated as factors affecting Scys-C in the elderly while gender, nephritis and kidney neoplasm were clarified as influencing factors in the young group. Scr levels were affected by more factors, such as body surface area and hematological disease. Correlation coefficient between rGFR and Scys-C or Scr showed that serum Scys-C was superior to Scr, especially in the subjects with mildly decreased renal function (−0.593 vs. −0.520).ConclusionsFactors other than renal function influenced Scys-C when applying to evaluate glomerular filtration rate (GFR), such as BMI, nephritis, kidney neoplasm and hypertension, and Scys-C had higher correlation with GFR than Scr in the elderly.

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