The Chronic Kidney Disease Epidemiology Collaboration equations perform less well in an older population with type 2 diabetes than their non-diabetic counterparts.

Objectives: The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations are based on creatinine alone (CKD-EPIcr), cystatin C alone (CKD-EPIcys) and combined creatinine and cystatin C (CKD-EPIcr-cys). It remains unclear whether these equations perform differently in older adults with type 2 diabetes than they do in non-diabetic older individuals. Methods: This single-center cross-sectional study was performed in adults aged ≥ 65 years between January 2019 and December 2021. Glomerular filtration rate (GFR) was measured by technetium-99m-diethylene triamine pentaacetic acid (99mTc-DTPA) renal dynamic imaging. The bias (difference between measured and estimated GFR), precision [interquartile range (IQR) of the median difference between measured GFR and estimated GFR] and accuracy P30 (percentage of estimated GFR within 30% of measured GFR) were considered the criteria of equation performance. Results: Finally, 476 participants were enrolled, including 243 adults with type 2 diabetes and 233 non-diabetic adults. The mean age of the included participants was 71.69 ± 6.4 years and 262 (55%) were male. The mean measured GFR was 49.02 ± 22.45 ml/min/1.73 m2. The CKD-EPIcr-cys equation showed significantly greater bias and lower accuracy (P30) in individuals with diabetes than in the non-diabetic group (median bias, 4.08 vs. 0.41 ml/min/1.73 m2, respectively, p < 0.05; P30, 63.78% vs. 78.54%, respectively, p < 0.05). The precision IQR indicated that CKD-EPIcr-cys had also lower precision in individuals with diabetes than in the non-diabetic controls (17.27 vs. 15.49 ml/min/1.73 m2, respectively). Similar results were observed for CKD-EPIcr and CKD-EPIcys equations. The P30 of all three equations failed to reach 80% in diabetic and non-diabetic groups. Conclusions: The performance of the CKD-EPI equations was lower in a group of patients aged ≥ 65 years with type 2 diabetes than in non-diabetic counterparts. However, each equation still had limitations regarding accuracy in older adults with or without diabetes.

A comparative study on the applicability of three CKD-EPI equations for estimation of glomerular filtration rate in Chinese patients with diabetic nephropathy / 中华肾脏病杂志

Objective To evaluate whether three chronic kidney disease epidemiology collaboration (CKD-EPI) equations (CKD-EPI2009Scr,CKD-EPI2012SCysC and CKD-EPI2012Scr-SCysC) are applicable in the prediction of glomerular filtration rate (GFR) in Chinese patients with diabetic nephropathy (DN).Methods One hundred and eight patients with DN who were hospitalized in the First Affiliated Hospital of Guangzhou Medical University with GFR being measured by dynamic renal imaging with 99mTc-DTPA from June 2012 to April 2014 were enrolled in this study.GFR measured by dynamic renal imaging with 99mTe-DTPA was used as the reference value (rGFR).GFR was estimated by the CKD-EPI2009Scr equation,the CKD-EPI2012SCySC equation,and the CKD-EPI2012Scr-SCysC equation (labeled as eGFR1,eGFR2,eGFR3).The correlation,30％ accuracy,staging consistency,deviation and diagnostic accuracy were compared among the three CKD-EPI equations.Results The rGFR in 108 DN patients was (61.78±26.51) ml· min-1· (1.73 m2)-1.The correlation between three eGFRs and rGFR was significant (all P ＜ 0.01),the correlation coefficients were 0.738,0.708,0.782.The 30％ accuracy were 74.07％,52.78％,67.59％,The 30％ accuracy of eGFR1 and eGFR3 were higher than eGFR2 (all P ＜ 0.05),but there was no significant difference between eGFR3 and eGFR1 (x2=0.874,P=0.436).The staging consistency was not ideal,Kappa values were 0.391,0.180 and 0.422.For the deviations between three eGFRs and rGFR,there was no significant difference between eGFR3 and rGFR (P ＞ 0.05),eGFR1 underestimated rGFR,eGFR2 overestimated rGFR (all P ＜ 0.01).The results of the Bland-Altman chart showed that consistencies between three eGFRs and rGFR were poor,the degree of deviation of eGFR3 was the smallest.The area under the ROC curve (AUC) of three eGFRs was 0.878,0.883 and 0.915.The AUC,sensitivity,specificity,overall compliance rate and Youden index of eGFR3 were the highest.Conclusions The eGFRs predicted by the three CKD-EPI equations showed good relevance,accuracy and diagnostic accuracy with the rGFR,but poor in consistencies.Comparatively,CKD-EPI2012Scr-SCysC may be better than others,but its consistency limits exceeds the acceptable limits.Therefore,the applicability of using the three CKD-EPI equations to predict the GFR in Chinese DN patients requires a larger sample and multiple verifications as well as further improvement.

Validation of a new standardized cystatin C turbidimetric assay: evaluation of the three novel CKD-EPI equations in hypertensive patients.

OBJECTIVES: Analytical and clinical performances of the new standardized cystatin C particle-enhanced turbidimetric immunoassay (PETIA) using DiaSys reagents on Olympus AU2700® analyzer were evaluated. DESIGN AND METHODS: We have studied imprecision, linearity, limit of detection and limit of quantification of this new immunoassay. Method comparison was assessed in relation to results generated by the standardized Siemens-particle-enhanced nephelometric immunoassay (PENIA). In order to evaluate the clinical relevance of this assay, estimated glomerular filtration rate (GFR) was calculated using MDRD, CKD-EPI creatinine, CKD-EPI cystatin C 2012 and CKD-EPI creatinine-cystatin C 2012 equations and compared to GFR measured using urinary clearance of (99m)Tc-DTPA in 100 hypertensive patients. RESULTS: Cystatin C measurements using DiaSys reagents have reliable analytical performances and are comparable to the standardized Siemens-PENIA method (bias of 0.01 mg/L). The mean measured GFR was 90.0±29.7 mL/min/1.73 m². Bias and accuracy of the three CKD-EPI equations were better than the MDRD. Both CKD-EPI creatinine-based and cystatin C-based formulae had similar bias, precision and accuracy. The combined creatinine-cystatin C equation was significantly more accurate and precise than the CKD-EPI creatinine equation in patients with GFR above 60 mL/min/1.73 m². CONCLUSIONS: The use of cystatin C in a combined equation with creatinine could improve the accuracy of eGFR in the reference interval.