Combined creatinine-cystatin C CKD-EPI equation significantly underestimates measured glomerular filtration rate in people with type 2 diabetes mellitus

Predictive performance of glomerular filtration rate equations based on cystatin C, creatinine and their combination in critically ill patients

OBJECTIVE

24-hour urine creatinine clearance (ClCr 24 hours) remains the gold standard for estimating glomerular filtration rate (GFR) in critically ill patients; however, simpler methods are commonly used in clinical practice. Serum creatinine (SCr) is the most frequently used biomarker to estimate GFR; and cystatin C, another biomarker, has been shown to reflect GFR changes earlier than SCr. We assess the performance of equations based on SCr, cystatin C and their combination (SCr-Cyst C) for estimating GFR in critically ill patients.

METHODS

Observational unicentric study in a tertiary care hospital. Patients with cystatin C, SCr and ClCr 24 hours measurements in ±2 days admitted to an intensive care unit were included. ClCr 24 hours was considered the reference method. GFR was estimated using SCr-based equations: Chronic Kidney Disease Epidemiology Collaboration based on creatinine (CKD-EPI-Cr) and Cockcroft-Gault (CG); cystatin C-based equations: CKD-EPI-CystC and CAPA; and Cr-CystC-based equations: CKD-EPI-Cr-CystC. Performance of each equation was assessed by calculating bias and precision, and Bland-Altman plots were built. Further analysis was performed with stratified data into CrCl 24 hours <60, 60-130 and ≥130 mL/min/1.73 m².

RESULTS

We included 275 measurements, corresponding to 186 patients. In the overall population, the CKD-EPI-Cr equation showed the lowest bias (2.6) and best precision (33.1). In patients with CrCl 24 hours <60 mL/min/1.73 m², cystatin-C-based equations showed the lowest bias (<3.0) and CKD-EPI-Cr-CystC was the most accurate (13.6). In the subgroup of 60≤ CrCl 24 hours <130mL/min/1.73 m², CKD-EPI-Cr-CystC was the most precise (20.9). However, in patients with CrCl 24 hours ≥130mL/min/1.73 m², cystatin C-based equations underestimated GFR, while CG overestimated it (22.7).

CONCLUSIONS

Our study showed no evidence of superiority of any equation over the others for all evaluated parameters: bias, precision and Lin's concordance correlation coefficient. Cystatin C-based equations were less biased in individuals with impaired renal function (GFR <60 mL/min/1.73 m²). CKD-EPI-Cr-CystC performed properly in patients with GFR from 60-130 mL/min/1.73 m² and none of them were accurate enough in patients ≥130 mL/min/1.73 m².

Optimal Glomerular Filtration Rate Equations for Various Age Groups, Disease Conditions and Ethnicities in Asia: A Systematic Review

(1) Background: The performance of estimated glomerular filtration rate (eGFR) equations in the Asian population has been widely questioned. The primary objective of this study was to gather evidence regarding optimal GFR equations in Asia for various age groups, disease conditions, and ethnicities. The secondary objective was to see whether the equations based on the combination of creatinine and cystatin C biomarkers if employed are satisfactory across different age groups and disease conditions in various ethnicities in Asia compared to those based on either of the single biomarkers. (2) Methods: Validation studies that had both creatinine and cystatin C-based equations either alone or in combination, validated in specific disease conditions, and those which compared the performance of these equations with exogenous markers were eligible only. The bias, precision, and 30% accuracy (P30) of each equation were recorded accordingly. (3) Results: Twenty-one studies consisting of 11,371 participants were included and 54 equations were extracted. The bias, precision, and P30 accuracies of the equations ranged from -14.54 to 9.96 mL/min/1.73 m2, 1.61 to 59.85 mL/min/1.73 m2, and 4.7% to 96.10%. The highest values of P30 accuracies were found for the JSN-CKDI equation (96.10%) in Chinese adult renal transplant recipients, for the BIS-2 equation (94.5%) in Chinese elderly CKD patients, and Filler equation (93.70%) also in Chinese adult renal transplant recipients. (4) Conclusions: Optimal equations were identified accordingly and it was proven that combination biomarker equations are more precise and accurate in most of the age groups and disease conditions. These can be considered equations of choice for the specific age groups, disease conditions, and ethnicities within Asia.

Estimated glomerular filtration rates are higher when creatinine-based equations are compared with a cystatin C-based equation in coronavirus disease 2019

OBJECTIVES

Estimations of glomerular filtration rate (eGFR) are based on analyses of creatinine and cystatin C, respectively. Coronavirus disease 2019 (COVID-19) patients in the intensive care unit (ICU) often have acute kidney injury (AKI) and are at increased risk of drug-induced kidney injury. The aim of this study was to compare creatinine-based eGFR equations to cystatin C-based eGFR in ICU patients with COVID-19.

METHODS

After informed consent, we included 370 adult ICU patients with COVID-19. Creatinine and cystatin C were analyzed at admission to the ICU as part of the routine care. Creatinine-based eGFR (ml/min) was calculated using the following equations, developed in chronological order; the Cockcroft-Gault (C-G), Modified Diet in Renal Disease (MDRD)1999, MDRD 2006, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), and Lund-Malmö revised (LMR) equations, which were compared with eGFR calculated using the cystatin C-based Caucasian Asian Pediatric Adult (CAPA) equation.

RESULTS

The median eGFR when determined by C-G was 99 ml/min and interquartile range (IQR: 67 ml/min). Corresponding estimations for MDRD1999 were 90 ml/min (IQR: 54); MDRD2006: 85 ml/min (IQR: 51); CKD-EPI: 91 ml/min (IQR: 47); and for LMR 83 ml/min (IQR: 41). eGFR was calculated using cystatin C and the CAPA equation value was 70 ml/min (IQR: 38). All differences between creatinine-based eGFR versus cystatin C-based eGFR were significant (p < .00001).

CONCLUSIONS

Estimation of GFR based on various analyses of creatinine are higher when compared with a cystatin C-based equation. The C-G equation had the worst performance and should not be used in combination with modern creatinine analysis methods for determination of drug dosage in COVID-19 patients.

Evaluation of the diagnostic performance of the creatinine-based Chronic Kidney Disease Epidemiology Collaboration equation in people with diabetes: A systematic review

AIMS

GFR estimated with the creatinine-based Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI_Cr ) equation is used to screen for diabetic kidney disease and assess its severity. We systematically reviewed the process and outcome of evaluating CKD-EPI_Cr in estimating point GFR or GFR decline over time in adults with type 1 or type 2 diabetes.

METHODS

In this systematic review, MEDLINE, Embase and Cochrane Central Register of Controlled Trials were searched up to August 2019. Observational studies comparing CKD-EPI_Cr with measured GFR (mGFR) in adults with diabetes were included. Studies on people with kidney transplant, non-diabetes related kidney disease, pregnancy, potential kidney donors, and those with critical or other systematic illnesses were excluded. Two independent reviewers extracted data from published papers and disagreements were resolved by consensus. Risk-of-bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. (PROSPERO registration number: CRD42018108776).

RESULTS

From the 2820 records identified, 29 studies (14 704 participants) were included. All studies were at risk of bias. Bias (eight different forms) ranged from -26 to 35 ml min^-1  1.73 m^-2 ; precision (five different forms) ranged between 9 and 63 ml min^-1  1.73 m^-2 ; accuracy (five different forms) ranged between 16% and 96%; the correlation coefficient between CKD-EPI_Cr and mGFR (four different forms) ranged between 0.38 and 0.86; and the reduced major axis regression slope ranged between 0.8 and 1.8.

CONCLUSIONS

Qualitative synthesis of data suggested CKD-EPI_Cr was inaccurate in estimating point GFR or GFR decline over time. Furthermore, a lack of consistency in the methods and processes of evaluating the diagnostic performance of CKD-EPI_Cr limits reliable quantitative assessment. The equation needs to be improved in adults with diabetes.

Comparison of bias and accuracy using cystatin C and creatinine in CKD-EPI equations for GFR estimation

BACKGROUND

The directly measured glomerular filtrate rate (mGFR) is the gold standard for kidney function, but it is invasive and costly. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations have been widely used to estimate GFR, however, the comparative accuracy of estimated GFR (eGFR) using creatinine and cystatin C in CKD-EPI equations remains unclear. We performed this meta-analysis to assess the bias and accuracy of eGFR using equations of CKD-EPI_crea, CKD-EPI_cys, and CKD-EPI_crea/cys in adult populations relevant to primary health care.

METHODS

Pubmed, Web of Science, EMBASE, and the Cochrane Library were searched from inception until December 2019 for related studies.

RESULTS

A total of 35 studies with 23,667 participants, which reported the data on the bias, and/or P30, and/or R were included. The difference in the bias of eGFR using CKD-EPI_cys was 4.84 mL/min/1.73 m² (95% CI, 1.88~7.80) lower than using CKD-EPI_crea, and 1.50 mL/min/1.73 m² (95% CI, 0.05~2.95) lower than using CKD-EPI_crea/cys. These gaps increased in subgroups of low mGFR (<60 mL/min/1.73 m²). CKD-EPI_crea/cys eGFR achieved the highest accuracy, 7.50% higher than CKD-EPI_crea (95% CI, 4.81~10.18), and 3.21% higher than CKD-EPI_cys (95% CI, -0.43~6.85); and the best correlation with mGFR, with Fisher's z transformed R of 1.20 (95% CI, 0.89-1.50).

CONCLUSIONS

CKD-EPI_crea/cys and CKD-EPI_cys gave less bias and more accurate estimates of mGFR than CKD-EPI_crea. More variables and coefficients could be added in CKD-EPI equations to achieve less bias and more accuracy in future research.

Diagnostic value of the Modification of Diet in Renal Disease and Chronic Kidney Disease Epidemiology Collaboration equations in diabetic patients: a systematic review and meta-analysis

BACKGROUND

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease (MDRD) equations are common for calculating estimated glomerular filtration rate (eGFR). Unlike CKD, the key pathological change of diabetic kidney disease (DKD) is glomerulosclerosis.

METHODS

To conduct a meta-analysis of the diagnostic performance of the CKD-EPI and MDRD equations in diabetic patients, we searched PubMed, Embase and the Cochrane Library for studies comparing standard GFR (sGFR) with eGFR using these two equations.

RESULTS

Thirteen studies of 7192 diabetic patients reporting data on bias or accuracy were included. At the study level, both equations underestimated eGFR. CKD-EPI was more accurate in studies with mean GFR ≥60 mL/minute/1.73 m². At the individual level, both equations overestimated GFR by 6.38 mL/minute/1.73 m² (95% confidence interval [CI] 2.67-10.1) and 7.65 mL/minute/1.73 m² (95% CI 2.78-12.52), respectively, for sGFR < 90 mL/minute/1.73 m². The CKD-EPI equation was 7.61% (95% CI 4.66-10.56) more accurate in subjects with sGFR > 90 mL/minute/1.73 m². The CKD-EPI equation performed poorly in diabetic patients.

CONCLUSIONS

The CKD-EPI equation can be used to estimate GFR in patients with incipient DKD, but has drawbacks. Improved eGFR equations suitable for diabetic populations are needed.

Performance of Cystatin C-Based Equations for Estimation of Glomerular Filtration Rate in Diabetes Patients: A Prisma-Compliant Systematic Review and Meta-Analysis

The accuracy of estimated glomerular filtration rate (eGFR) equations in diabetes mellitus (DM) patients has been extensively questioned. We evaluated the performance of cystatin C-based equations alone or in combination with creatinine to estimate GFR in DM patients. A PRISMA-compliant systematic review was performed in the MEDLINE and Embase databases, with “diabetes mellitus” and “cystatin C” as search terms. Studies comparing cystatin C-based eGFR equations with measured GFR (mGFR) in DM patients were eligible. Accuracies P10, P15, P20, and P30 indicated the proportion of eGFR results within 10, 15, 20, and 30% of mGFR. Single-arm meta-analyses were conducted, and the Quality of Diagnostic Accuracy Studies-II tool (QUADAS-2) was applied. Twenty-three studies comprising 7065 participants were included, and 24 equations were analyzed in a broad range of GFRs. Meta-analyses were completed for 10 equations. The mean P30 accuracies of the equations ranged from 41% to 87%, with the highest values found with both CKD-EPI equations. Mean P10-P15 achieved 35% in the best scenario. A sensitivity analysis to evaluate different mGFR methods did not change results. In conclusion, cystatin C-based eGFR equations represent measured GFR fairly at best in DM patients, with high variability among the several proposed equations.

Influence of age, gender, smoking, diabetes, thyroid and cardiac dysfunctions on cystatin C biomarker

BACKGROUND

Creatinine is the most widely used renal failure biomarker; however, it has a lot of drawbacks. One of the major drawbacks is the blind range (does not increase until 50% of the kidney deteriorates). On the other hand, cystatin C has gained more attention as a promising biomarker due to several advantages over creatinine. Cystatin C levels are elevated as soon as any mild defect in the kidney occurs. Furthermore, cystatin C is influenced by several non-renal diseases which provide an additional prognostic value for this promising biomarker.

OBJECTIVES

1. Study the effects of age, gender and smoking on cystatin C levels to. 2. Challenge the adoption of glomerular filtration rate equations for healthy population. 3. Compare the values generated from different glomerular filtration rate equations. 4. Evaluate the prognostic value of cystatin C for selected non-renal diseases.

METHODS

Using cross sectional analyses, we established the relationship between cystatin C levels and non-renal predictors. The quantification of cystatin C was performed by high performance liquid chromatographic method, while for creatinine by a colorimetric enzymatic method.

RESULTS

In the healthy volunteers the levels of cystatin C were slightly higher in men than in women and in individuals older than 50 years old than those under 50 years old and in smokers than non-smokers, however, statistical data confirmed a non-significant relationship with respect to the aforementioned factors. For the recruited patients suffering from (diabetes, hyper- and hypothyroidism and cardiac dysfunctions) a clear increase in cystatin C levels were observed with the exception of hypothyroidism patients in which a decrease in their cystatin C levels were observed.

CONCLUSION

Diabetes, thyroid and cardiac dysfunctions have a clear impact on the levels of cystatin C in human blood, whereas age, gender and smoking habit have no effect. Therefore, cystatin C could be considered as a useful biomarker of the aforementioned diseases, in turn, this requires extra precautions including the evaluation of several clinical conditions by physicians should CC is considered as a renal failure biomarker.