Evaluation of the CKD-EPI 2021 creatinine equation using laboratory data: Considerations for practice changes among clinical laboratories in British Columbia, Canada

INTRODUCTION

Clinical laboratories in British Columbia, Canada implemented the CKD-EPI 2009 equation without the race variable for estimated glomerular filtration rate (eGFR) reporting since 2014. As more clinical laboratories adopt the new CKD-EPI 2021 equation, the study aims to compare these two race-free CKD-EPI eGFR equations using the laboratory data from a large tertiary hospital in BC and evaluate the impact on reclassification of eGFR category.

METHODS

Serum/plasma creatinine results and demographic data were collected from Vancouver General Hospital laboratory. The CKD-EPI 2009 without the race variable and CKD-EPI 2021 equations were computed. eGFR and its distributions were compared and reclassification of eGFR category was assessed across the full cohort and in specific patient populations.

RESULTS

The analysis included 58,763 patients. The median age was 57 years, with women comprising 51 % of the population. The median of eGFR changed from 85 to 90 mL/min/1.73 m2 using the CKD-EPI 2009 equation without the race variable and the CKD-EPI 2021 equation, respectively. The CKD-EPI 2021 equation reclassified 11.86 % of patients, mainly from G3a (45-59 mL/min/1.73 m2) to G2 (60-89 mL/min/1.73 m2). There was statistical significance between the non-renal and the renal population reclassified from G5 (<15 mL/min/1.73 m2) to G4 (15-29 mL/min/1.73 m2).

CONCLUSIONS

Using laboratory data representative of local populations, we observed an overall positive shift to higher eGFR, with 11.86 % of individuals having improved eGFR categories based on the CKD-EPI 2021 equation. This study provides insights into clinical implications at both the individual and population levels. The data-based approach is the first step towards adopting the CKD-EPI 2021 equation within the province.

Performance of the race-free CKD-EPI creatinine-based eGFR equation in a Danish cohort with measured GFR

Background

In 2021, an updated Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation for estimated glomerular filtration rate (eGFR) without a coefficient for race (CKD-EPI21) was developed. The performance of this new equation has yet to be examined among specific patient groups.

Methods

We compared the performances of the new CKD-EPI21 equation and the 2009 equation assuming non-Black race (CKD-EPI09-NB) in patients with GFR measured by chromium-51-EDTA plasma clearance at Aarhus University Hospital in Denmark during 2010-18. We examined bias, accuracy, precision and correct classification of chronic kidney disease (CKD) stage using chromium-51-EDTA clearance as the reference standard. We assessed the performance in the total cohort, cancer patients and potential living kidney donors. We also assessed the performance stratified by CKD stage in the total cohort.

Results

In this predominantly white population, the CKD-EPI21 equation performed slightly better than the CKD-EPI09-NB equation in both the total cohort (N = 4668), and in cancer patients (N = 3313) and potential living kidney donors (N = 239). In the total cohort, the CKD-EPI21 equation demonstrated a slightly lower median absolute bias (-0.2 versus -4.4 mL/min/1.73 m2), and a similar accuracy, precision and correct classification of CKD stage compared with the CKD-EPI09-NB equation. When stratified by CKD stage, the CKD-EPI09-NB equation performed slightly better than the CKD-EPI21 equation among patients with a measured GFR (mGFR) <60 mL/min/1.73 m2.

Conclusions

In a selected cohort of Danish patients with mGFR, the CKD-EPI21 equation performed slightly better than the CKD-EPI09-NB equation except for patients with a mGFR <60 mL/min/1.73 m2, where CKD-EPI09-NB performed slightly better although the differences were considered clinically insignificant.

Average creatinine-urea clearance: revival of an old analytical technique?

Background

Creatinine-based equations such as the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) are recommended for estimating glomerular filtration rate (eGFR) in clinical practice, but have reduced performance in advanced stages of chronic kidney disease. However, only rarely studies have evaluated the performance of eGFR by measuring the average of the urinary clearances of creatinine and urea (mCl_UN-cr) compared with the eGFR equations.

Methods

This cross-sectional study evaluated the usefulness of mCl_UN-cr in a population of 855 participants who performed a GFR measurement by urinary inulin clearance. The performance of mCl_UN-cr was compared with those of CKD-EPI 2009 and CKD-EPI 2021, considering three criteria: bias, precision and accuracy.

Results

In the whole sample, the mCl_UN-cr performed similarly to CKD-EPI equations (2009 and 2021) [precision: 11.5 (95% CI 10.5; 12.5) vs 19.0 (95% CI 17.2; 20.1) and 19.1 (95% CI 17.4; 20.4), and accuracy P₃₀: 97.0 (95% CI 95.8; 98.0) vs 82.0 (95% CI 79.2; 84.4) and 77.2 (95% CI 74.5; 80.0)]. The CKD-EPI equations (2009 and 2021) had the best performance when mGFR was >60 mL/min/1.73 m². In contrast, the mCl_UN-cr performed better than others with lowest mGFR values, more noticeable when mGFR was <60 mL/min/1.73 m².

Conclusions

The study described the best performance of mCl_UN-cr at GFR levels below 60 mL/min/1.73 m² and a satisfactory result in the overall cohort. The findings point to a role of this tool, especially for estimating GFR in chronic kidney disease patients in developing countries, when reference measurement of GFR is not available.

Is the use of the new Chronic Kidney Disease Epidemiology Consortium (CKD-EPI 2021) formula appropriate for the Spanish population?

INTRODUCTION

United States nephrology societies recommend changing from the CKD-EPI 2009 equation to the new CKD-EPI 2021 equation, which does not include the race coefficient, for calculating estimated glomerular filtration rate (eGFR). It is unknown how this change might affect the distribution of kidney disease in the predominantly Caucasian Spanish population.

METHODS

Two databases of adults from the province of Cádiz, DB-SIDICA (N=264,217) and DB-PANDEMIA (N=64,217), that had plasma creatinine measurements recorded between 2017 and 2021 were studied. Changes in eGFR and the consequent reclassification into different categories of the KDIGO 2012 classification resulting from substituting the CKD-EPI 2009 equation for the 2021 equation were calculated.

RESULTS

Compared to the 2009 equation, CKD-EPI 2021 yielded a higher eGFR, with a median of 3.8mL/min/1.73m² (IQR 2.98-4.48) in DB-SIDICA and 3.89mL/min/1.73m² (IQR 3.05-4.55) in DB-PANDEMIA. The first consequence was that 15.3% of the total population in DB-SIDICA and 15.1% of the total population in DB-PANDEMIA were reclassified into a higher category of eGFR, as were 28.1% and 27.3%, respectively, of the population with CKD (G3-G5); no subjects were classified into the more severe category. The second consequence was that the prevalence of kidney disease decreased from 9% to 7.5% in both cohorts.

CONCLUSIONS

Implementing the CKD-EPI 2021 equation in the Spanish population, which is predominantly Caucasian, would increase eGFR by a modest amount (greater in men and those who are older or have a higher GFR). A significant proportion of the population would be classified into a higher eGFR category, with a consequent decrease in the prevalence of kidney disease.

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.

Kidney disease burden in an Asian Indian population: Effect of the new 2021 serum creatinine CKD-EPI equation

AIMS

CKD-EPI (chronic kidney disease-epidemiological) serum creatinine equation is widely accepted for calculating estimated glomerular filtration rate (eGFR). The effect of transitioning from the older 2009 to the newer race-independent 2021 CKD-EPI equation on the estimated kidney disease burden (eKDB) was studied in an Asian-Indian population.

METHODS

The study included 1156 adults, the two equations were compared for agreement (Bland-Altman and Cohen's kappa) and concordance (Lin's correlation and test for proportions).

RESULTS

The 2021 CKD-EPI increased the eGFR (positive-bias), independent of age-group, gender or presence of type 2 diabetes mellitus (T2DM) and hypertension (HTN). Thus, the eKDB was significantly decreased by 2021 CKD-EPI equation. The agreement was highest for the age-group 31-40 years (95.8 % versus 87.5 % for > 50 years). Besides, the eGFR category was shifted from G3 to G1 in 8.2 % (95 % CI: 6.8-9.9) individuals by 2021 CKD-EPI. The effect of transition on eKDB was greater in individuals > 50 years (7.4 %) or with HTN (6.3 %).

CONCLUSION

In comparison to the old equation, the 2021 CKD-EPI equation increased the eGFR, lowering the eKDB in this Asian-Indian cohort. The degree of lowering was affected by age-group, and presence of T2DM /HTN, but independent of gender.

The Glomerular Filtration Rate: From the Diagnosis of Kidney Function to a Public Health Tool

The prevalence of chronic kidney disease (CKD) continues to increase worldwide, as well as the associated morbidity and mortality and the consequences on the patients' quality of life and countries' economies. CKD often evolves without being recognized by patients and physicians, although the diagnosis is based on two simple laboratory data: the estimated glomerular filtration rate (eGFR) and urine analysis. To measure GFR, the knowledge about the physiologic processes at the nephron level, the concept of clearance, and the identification of creatinine as a suitable endogenous marker for measuring the creatinine clearance (CrCl) had to be previously developed. On those bases, different equations to calculate CrCl (Cockcroft and Gault, 1976), or estimated GFR (four variables MDRD, 1999; CKD-Epi, 2009, among others) were generated. They all include creatinine and some demographic data, such as sex and age. However, to compare results throughout life or among laboratories, the creatinine determination must be standardized. In addition, the accuracy of these equations remains controversial in certain subgroups of patients. For these reasons, other mathematical models to improve CrCl estimation have been developed, such as when urine cannot be collected, in debilitated elderly patients and patients with trauma, diabetes, or obesity. Currently, eGFR in adults can be measured and reported immediately, using isotope dilution mass spectrometry traceable creatinine-based equations. In conclusion, based on knowledge obtained from renal physiology, eGFR can be used in the clinic for the diagnosis and early treatment of CKD, as well as a public instrument to estimate the prevalence.

Assessment of Pre-Donation Glomerular Filtration Rate: Going Back To Basics A Position Paper from the DESCARTES Working Group of the ERA-EDTA

The 2017 version of the KDIGO (Kidney Disease: Improving Global Outcomes) guidelines is the most recent international framework for the evaluation and care of living kidneys donors. Along with the call for an integrative approach evaluating the long-term end-stage kidney disease risk for the future potential donor, several recommendations are formulated regarding the predonation glomerular filtration rate (GFR) adequacy with no or little consideration for the donor candidate's age and for the importance of using reference methods of GFR measurements. Herein, we question the position of the KDIGO guidelines and discuss the rationale and modalities for a more basic, but not less demanding GFR evaluation susceptible to enable a more efficient selection of the potential kidney donor.

Prevalence and determinants of chronic kidney disease in urban adults' populations of northern Cameroon

BACKGROUND

Chronic kidney disease (CKD) is a major health problem with growing prevalence in sub-Saharan Africa.

AIM

Assess the prevalence and determinants of CKD in Garoua and Figuil cities of the North region of Cameroon.

METHODS

A cross-sectional survey was conducted from January to June 2018 in the two cities, using a multi-level cluster sampling. All adults with low estimated glomerular filtration rate (eGFR) (< 60 ml/min/1.73 m²) by Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and/or albuminuria (≥ 30 mg/g) were reviewed three months later. Logistic regression models (accounting for the sampling strategy) were used to investigate the predictors of the outcomes.

RESULTS

A total of 433 participants were included, with a mean age (95%CI) of 45.0 (43.4-46.6) years, 212 (48.7%) men, 294 (67.9%) from Garoua and 218 (45.6%) with no formal education. Risk factors for chronic nephropathy were highly prevalent including longstanding use of street medications (52.8%), herbal medicines (50.2%) and non-steroidal anti-inflammatory drugs (50%), alcohol consumption (34.4%), hypertension (33.9%), overweight/obesity (33.6%), hyperuricemia (16.8%), smoking (11.3%) and hyperglycemia (6.5%). The prevalence of CKD was 11.7% overall, 10.7% in Garoua and 13% in Figuil participants. Equivalents figures for CKD G3-5 and albuminuria were 2.8%, 2.0% and 4.5%; and 9.1%, 9.3% and 8.5%, respectively. History of diabetes, increase systolic blood pressure, hyperglycemia and hyperuricemia were predictors of CKD.

CONCLUSION

The prevalence of CKD is as high in these northern cities as previously reported in southern cities of Cameroon, driven mostly by known modifiable risk factors of chronic nephropathy.

Performance of 4 Creatinine-based Equations in Assessing Glomerular Filtration Rate in Adults with Diabetes

AIMS

To evaluate diagnostic performance of glomerular filtration rate (GFR) estimated by modification of diet in renal disease (MDRD), chronic kidney disease epidemiology collaboration (CKD-EPI), full age spectrum (FAS), and revised Lund-Malmö (r-LM) equations in adults with diabetes.

METHODS

Individuals were included in this cross-sectional study if they had at least 1 measurement of technetium-99m diethylenetriamine-pentaacetic acid (99mTc-DTPA) GFR (mGFR) and serum creatinine (1487 patients with 2703 measures). GFR calculated by estimation equations was compared with mGFR. Diagnostic performance was assessed using concordance correlation coefficient (CCC), bias, precision, accuracy, reduced major axis regression (RMAR), and Bland-Altman plot. Analysis was repeated in subgroups based on sex, diabetes type, Hemoglobin A1C, and GFR level.

RESULTS

Of all patients, 1189 (86%) had type 2 diabetes. Mean mGFR, MDRD, CKD-EPI, FAS, and revised Lund-Malmö eGFR were 66, 72, 74, 71, and 67 mL/min/1.73m2, respectively. Overall, the r-LM had the highest CCC (0.83), lowest bias (-1.4 mL/min/1.73 m2), highest precision (16.2 mL/min/1.73 m2), and highest accuracy (P10 = 39%). The RMAR (slope, intercept) in r-LM, FAS, MDRD, and CKD-EPI was 1.18, -13.35; 0.97, -2.9; 1, -6.4, and 1.04, -11.3, respectively. The Bland-Altman plot showed that r-LM had the lowest mean difference and the narrowest 95% limit of agreement (-1.0, 54.1 mL/min/1.73 m2), while mean difference was more than 5-fold higher in FAS, MDRD, and CKD-EPI (-5.2, -6.3, and -8.2, respectively).

CONCLUSIONS

In adults with diabetes the revised Lund-Malmö performs better than MDRD, CKD-EPI, and FAS in calculating point estimates of GFR.

Recurrent acute kidney injury: predictors and impact in a large population-based cohort

BACKGROUND

This study examined the impact of recurrent episodes of acute kidney injury (AKI) on patient outcomes.

METHODS

The Welsh National electronic AKI reporting system was used to identify all cases of AKI in patients ≥18 years of age between April 2015 and September 2018. Patients were grouped according to the number of AKI episodes they experienced with each patient's first episode described as their index episode. We compared the demography and patient outcomes of those patients with a single AKI episode with those patients with multiple AKI episodes. Analysis included 153 776 AKI episodes in 111 528 patients.

RESULTS

Of those who experienced AKI and survived their index episode, 29.3% experienced a second episode, 9.9% a third episode and 4.0% experienced fourth or more episodes. Thirty-day mortality for those patients with multiple episodes of AKI was significantly higher than for those patients with a single episode (31.3% versus 24.9%, P < 0.001). Following a single episode, recovery to baseline renal function at 30 days was achieved in 83.6% of patients and was significantly higher than for patients who had repeated episodes (77.8%, P < 0.001). For surviving patients, non-recovery of renal function following any AKI episode was significantly associated with a higher probability of a further AKI episode (33.4% versus 41.0%, P < 0.001). Furthermore, with each episode of AKI the likelihood of a subsequent episode also increased (31.0% versus 43.2% versus 51.2% versus 51.7% following a first, second, third and fourth episode, P < 0.001 for all comparisons).

CONCLUSIONS

The results of this study provide an important contribution to the debate regarding the need for risk stratification for recurrent AKI. The data suggest that such a tool would be useful given the poor patient and renal outcomes associated with recurrent AKI episodes as highlighted by this study.

Relationship between decline in estimated or measured glomerular filtration rate and 16-year postrenal transplant outcome

Background

Glomerular filtration rate (GFR) decline ≥30% over 2 years can substitute for the conventional ‘doubling of serum creatinine’ to predict end-stage renal disease in patients with native kidneys. While chronic kidney disease trajectory is less predictable in transplanted patients, recent data have suggested that similar GFR decline might be an acceptable surrogate for long-term transplant outcome. We sought (i) to confirm the prognostic value of an early GFR decline in kidney transplant recipients and (ii) to determine whether using direct measurement of GFR with inulin improves the performance of this surrogate.

Methods

We retrospectively analysed all recipients transplanted between 1989 and 2000 in our centre, with inulin-measured and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)-estimated GFR at 1 and 5 years post-transplant, and evaluated the performance [time-dependent area under the receiver operating characteristic curve (ROC AUC) and subdistribution hazard ratio (sdHR) with competing risk model] of GFR change to predict graft failure and all-cause mortality.

Results

Out of 417 kidney transplant recipients, 116 patients had lost their graft and 77 had died 16 years after transplantation. While being significantly associated with graft failure [sdHR = 2.37 (95% confidence interval 1.47–3.83)], CKD-EPI-GFR decline ≥30% failed to appropriately predict long-term graft survival (C-statistics of 0.63). Concordance between inulin-GFR and CKD-EPI-GFR to detect similar GFR change was only 53%. Inulin-GFR change was, however, not a better predictor (C-statistics of 0.59). Comparable results were observed for mortality.

Conclusions

Our data suggest that early GFR decline is a poor surrogate for long-term transplant outcome, even when change in GFR is directly measured by a reference method.

Estimation of glomerular filtration rate from skeletal muscle mass. A new equation independent from age, weight, gender, and ethnicity

BACKGROUND AND AIMS

The most used indicator for the renal function is the glomerular filtration rate (GFR). Current used predictive GFR equations were calibrated on patients with chronic kidney disease. Thus, they are not very precise in healthy individuals. The estimation of skeletal muscle mass (SMM) allows the prediction of the daily urinary creatinine excretion (24hUCrE). This study proposes an equation for the estimation of GFR based on SMM (eGFRMuscle) and serum creatinine (SCr).

METHODS AND RESULTS

Four hundred sixty-six free-living men underwent a bioelectrical impedance analysis for the evaluation of SMM (kg), a blood withdrawal for the measurement of SCr (mg/dL), and a 24-h urinary collection for the assessment of 24hUCrE (g/24 h). The linear regression analysis between SMM and 24hUCrE and the measurement of SCr allowed developing a predictive equation of eGFRMuscle. The equation predicting eGFRMuscle (ml/min/1.73 m²) was SMM (kg) × 3.06/SCr (mg/dL). eGFRMuscle was statistically different from eGFR predicted by Cockroft-Gault, MDRD Study, and CKD-EPI equations (p = 0.017, p < 0.001, and p < 0.001, respectively). Pairwise comparison of standard error of the area under the ROC curve (AUC) of eGFRMuscle with all the other AUCs of ROC curves highlighted significant differences.

CONCLUSIONS

The equation presented in this study results in age, weight, gender, and ethnicity independent because it arises directly from SMM estimation. Therefore, the proposed equation could allow evaluating the GFR also in healthy people with low, average, or high weight, and in older people, regardless of GFR and SCr levels.

The practicality of different eGFR equations in centenarians and near-centenarians: which equation should we choose?

Background

No studies have examined the practicality of the Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiological Collaboration (CKD-EPI) and Berlin Initiative Study 1 (BIS1) equations for the estimated glomerular filtration rate (eGFR) in a large sample of centenarians. We aim to investigate the differences among the equations and suggest the most suitable equation for centenarians and near-centenarians.

Methods

A total of 966 centenarians and 787 near-centenarians were enrolled, and the eGFR was calculated using the three equations mentioned above. Agreement among the equations was investigated with the κ statistic and Bland-Altman plots. Sources of discrepancy were investigated using a partial correlation analysis.

Results

The three equations for assessing eGFR are not considered interchangeable in centenarians and near-centenarians. Δ(MDRD, CKD-EPI) and Δ(MDRD, BIS1) increased with age, but Δ(CKD-EPI, BIS1) was relatively stable with age. Δ(MDRD, CKD-EPI) and Δ(MDRD, BIS1) were considerable in subjects with Scr levels less than 0.7 mg/dL and decreased with the Scr level. A considerable difference between CKD-EPI and BIS1 was observed for participants with Scr levels ranging from 0.5 to 1.5 mg/dL. This difference increased with Scr levels ranging from 0.5 to 0.7 mg/dL, was relatively stable for Scr levels ranging from 0.7 to 0.9 mg/dL, and decreased with Scr levels ranging from 0.9 to 1.5 mg/dL. The differences in the three comparisons were all greater in women than in men (p < 0.05).

Conclusions

We tend to suggest the MDRD equation to calculate the glomerular filtration rate (GFR) in elderly individuals >95 years old who have no risk factors for cardiovascular disease; the BIS1 equation to calculate the eGFR for elderly individuals younger than 94 years old who have risk factors for cardiovascular disease; the CKD-EPI equation to calculate the eGFR of elderly individuals with Scr levels greater than 1.5 mg/dL; and the BIS1 equation to calculate the eGFR of older women with Scr levels less than 0.7 mg/dL.

Evaluation of discriminative capacity of two formulas of CKD-EPI to predict complications after the first episode of heart failure with preserved ejection fraction

Background: Determining the prognosis of heart failure with preserved ejection fraction (HFpEF) is problematic, as the ejection fraction cannot be used. Formulae that estimate glomerular filtration rate (eGFR) may be potential prognosticators for this condition, since renal dysfunction is a well-known predictor of poor outcomes of all forms of heart failure.

Methods: A prospective observational study of 117 HFpEF patients (average age 71.6±9.1 years; 65.8% women) who had eGFR determined after their first episode of cardiac decompensation by two different chronic kidney disease epidemiology collaboration (CKD-EPI) equations. The ability to predict hospitalizations and mortality over 24 months by the two equations were compared.

Results: The CKD-EPI formula based on serum creatinine only performed poorly. However, the CKD-EPI equation that used both serum creatinine and serum cystatin C was associated with unfavorable outcome: eGFR <45 mL/min/1.73 m² predicted 24-month mortality (HR=4.21 [1.32;13.43], p=0.02) and the combined endpoint of mortality and hospitalization (HR 2.45 [1.42;4.22], p=0.001). .

Conclusions: eGFR by the CKD-EPI equation based on serum creatinine and cystatin C levels, but not by the CKD-EPI creatinine only equation, predicts the outcome of HFpEF patients.

Comparison of the Cockcroft-Gault, MDRD and CKD-EPI equations for estimating ganciclovir clearance

AIMS

Accurately estimating kidney function is essential for the safe administration of renally cleared drugs such as ganciclovir. Current practice recommends adjusting renally eliminated drugs according to the Cockcroft-Gault equation. There are no data on the utility of the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in ganciclovir dosing. To evaluate which renal function equation best predicts ganciclovir clearance.

METHODS

The performance of the Cockcroft-Gault equation, isotope dilution mass spectrometry (IDMS)-traceable 4-variable MDRD study (MDRD4-IDMS) equation and CKD-EPI equation in determining ganciclovir clearance were assessed retrospectively in patients treated with ganciclovir from 2004-2015. The MDRD4-IDMS and CKD-EPI equations adjusted to individual body surface area (MDRD4-IDMS·BSA and CKD-EPI·BSA, respectively) were also evaluated. Patients with intravenous ganciclovir peak and trough concentrations in their medical records were included in the study. Ganciclovir clearance was calculated from serum concentrations using a one-compartment model. The five equations were compared based on their predictive ability, the coefficient of determination, through a linear regression analysis. The results were validated in a group of patients.

RESULTS

One hundred patients were included in the final analysis. Seventy-four patients were analysed in the learning group and 26 in the validation group. The coefficient of determination was 0.281 for Cockcroft-Gault, 0.301 for CKD-EPI·BSA, 0.308 for MDRD4-IDMS·BSA, 0.324 for MDRD4-IDMS and 0.360 for CKD-EPI. Subgroup analysis also showed that CKD-EPI is a better predictor of ganciclovir clearance. Analysis of the validation group confirmed these results.

CONCLUSIONS

The CKD-EPI equation correlates better with ganciclovir clearance than the Cockcroft-Gault and MDRD4-IDMS equations, even the clinical difference between the equations is scarce.

Comparison of equations for dosing of medications in renal impairment

AIM

The aim of this study is to determine the concordance among the Cockcroft-Gault, the Modification of Diet in Renal Disease and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in hypothetical dosing of renally cleared medications.

METHODS

A total of 2163 patients prescribed at least one of the 31 renally cleared drugs under review were included in the study. Kidney function was estimated using the three equations. We compared actual prescribed dosages of the same drug with recommended dosages based on the kidney function as calculated by each of the equations and applying dosing recommendations in the Australian Medicines Handbook.

RESULTS

There was a significant difference in the kidney function values estimated from the three equations (P < 0.001). Despite the good overall agreement in renal drug dosing, we found selected but potentially important discrepancies among the doses rendered from the equations. The CKD-EPI equation non-normalized for body surface area had a greater rate of concordance with the Cockcroft-Gault equation than the Modification of Diet in Renal Disease equation for renal drug dosing.

CONCLUSIONS

There is need for a long-term multi-centre study in a diverse population to define the clinical effects of the discrepancies among the equations for drug dosing. Given the greater concordance of the non-normalized CKD-EPI equation with the Cockcroft-Gault equation for dosing, the recommendation by Kidney Health Australia and the United States National Kidney Disease Education Program that 'dosing based on either eCrCl or an eGFR with body surface area normalization removed are acceptable' seems suitable and practicable for the purpose of dosing of non-critical drugs in the primary care setting.

Clinical characteristics, complications and management of patients with type 2 diabetes with and without diabetic kidney disease (DKD): A comparison of data from a clinical database

BACKGROUND AND OBJECTIVES

The main objective of this study was to assess the percentage of co-morbid nephropathy in type 2 diabetes patients using the CKD-EPI equation and to compare the clinical characteristics and treatments of patients with type 2 diabetes with nephropathy with those of patients without nephropathy PATIENTS AND METHODS: This was a cross-sectional analysis of the demographic and clinical data registered in the IDIBAPS Biobank database. Patients were considered to have nephropathy if the diagnosis was reported in their clinical history, albuminuria (>30 mg/g) was indicated as present in the last urine test available, or an estimated glomerular filtration rate (eGFR) below 60 ml/min/1.73 m² was calculated using the CKD-EPI equation.

RESULTS

Clinical data were obtained from 1,397 patients with a diagnosis of type 2 diabetes. The percentage of patients with nephropathy was 29.3% (N= 369) (95% confidence interval, 26.8% to 31.9%); however, only 109 (7.8%) patients had a nephropathy diagnosis reported in their clinical history. Compared with patients without nephropathy, patients with nephropathy have a higher mean age, higher frequency of diabetes complications and received insulin more frequently.

CONCLUSION

Our results show that the percentage of type 2 diabetes patients with nephropathy was high and that this comorbidity was associated with a significantly higher frequency of diabetes macro- and microvascular complications (compared to diabetes patients without DKD).

Monitoring the estimated glomerular filtration rate (eGFR) in patients with small-cell lung cancer during chemotherapy: equations based on serum creatinine or cystatin C?

BACKGROUND

This study compared the differences between the estimated glomerular filtration rate (eGFR) calculated by several equations based on serum creatinine (Scr) and cystatin C (CysC) concentrations for monitoring renal function in patients with small-cell lung cancer (SCLC) during chemotherapy.

METHODS

Seventy-one patients with SCLC were retrospectively analyzed. The eGFR before and after each chemotherapy cycle was calculated by the following equations: the chronic kidney disease epidemiology collaboration (CKD-EPI) equation, the modification of diet in renal disease (MDRD) equation, the Cockcroft-Gault (CG) equation, and five CysC-based equations. The patients were compared among the different eGFR groups.

RESULTS

The mean decreases in eGFR_CKD-EPI (-2.25 ± 9.89 ml/min/1.73 m²) between each treatment cycle were more significant than the decreases in eGFR_CG (-0.46 ± 10.17 ml/min/1.73 m²), eGFR_MDRD (-0.48 ± 9.79 ml/min/1.73 m²), and five calculated eGFR_CysC (p < 0.05). Single-/multiparameter analyses showed that patients with a higher body mass index (BMI >23) and receiving more treatment cycles (>3) were at increased risk for developing renal impairment with an eGFR less than 60 ml/min/1.73 m² during chemotherapy.

CONCLUSIONS

The eGFR calculated by the CKD-EPI equation changed more significantly between each chemotherapy cycle than did the eGFR from the other equations based on Scr or CysC in patients with SCLC. Oncologists should pay more attention to the renal function of specific patient groups during treatment.

Prevalence of chronic kidney disease and association with cardiovascular risk factors among teachers in Cape Town, South Africa

Background: There is a need to determine the feasibility of conducting studies of chronic diseases among large cohorts of African patients. One aim of the South African feasibility study was to determine the prevalence of chronic kidney disease (CKD) and its association with cardiovascular disease (CVD) risk factors among school teachers. Methods: In a cross-sectional survey of 489 teachers we captured data on demographics, CVD risk factors, anthropometry and blood pressure. Serum glucose, creatinine, cholesterol and urine protein/creatinine ratio was measured. Glomerular filtration rate was estimated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and the Modification of Diet in Renal Disease study equations. Results: The mean (± standard deviation) age of the participants was 46.3 ± 8.5 years, with 70.3% being female and 74.6% of mixed ethnicity. The crude prevalence of CKD using the CKD-EPI equation was 6.1% while the age-adjusted prevalence was 6.4% (95% confidence interval 3.2-9.7%). CKD was associated with the presence of diabetes and higher diastolic blood pressures. Conclusions: In our study population of relatively young, working individuals CKD was common, clinically silent and associated with cardiovascular risk factors. The long-term complications of CKD are serious and expensive to manage and this, therefore, constitutes an important public health problem for South Africa.

Comparing Results of Five Glomerular Filtration Rate-Estimating Equations in the Korean General Population: MDRD Study, Revised Lund-Malmö, and Three CKD-EPI Equations

Background

Estimated glomerular filtration rate (eGFR) is a widely used index of kidney function. Recently, new formulas such as the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations or the Lund-Malmö equation were introduced for assessing eGFR. We compared them with the Modification of Diet in Renal Disease (MDRD) Study equation in the Korean adult population.

Methods

The study population comprised 1,482 individuals (median age 51 [42-59] yr, 48.9% males) who received annual physical check-ups during the year 2014. Serum creatinine (Cr) and cystatin C (CysC) were measured. We conducted a retrospective analysis using five GFR estimating equations (MDRD Study, revised Lund-Malmö, and Cr and/or CysC-based CKD-EPI equations). Reduced GFR was defined as eGFR <60 mL/min/1.73 m².

Results

For the GFR category distribution, large discrepancies were observed depending on the equation used; category G1 (≥90 mL/min/1.73 m²) ranged from 7.4-81.8%. Compared with the MDRD Study equation, the other four equations overestimated GFR, and CysC-based equations showed a greater difference (-31.3 for CKD-EPI_CysC and -20.5 for CKD-EPI_Cr-CysC). CysC-based equations decreased the prevalence of reduced GFR by one third (9.4% in the MDRD Study and 2.4% in CKD-EPI_CysC).

Conclusions

Our data shows that there are remarkable differences in eGFR assessment in the Korean population depending on the equation used, especially in normal or mildly decreased categories. Further prospective studies are necessary in various clinical settings.

Comparison of creatinine and cystatin C based eGFR in the estimation of glomerular filtration rate in Indigenous Australians: The eGFR Study

BACKGROUND

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation that combines creatinine and cystatin C is superior to equations that include either measure alone in estimating glomerular filtration rate (GFR). However, whether cystatin C can provide any additional benefits in estimating GFR for Indigenous Australians, a population at high risk of end-stage kidney disease (ESKD) is unknown.

METHODS

Using a cross-sectional analysis from the eGFR Study of 654 Indigenous Australians at high risk of ESKD, eGFR was calculated using the CKD-EPI equations for serum creatinine (eGFRcr), cystatin C (eGFRcysC) and combined creatinine and cystatin C (eGFRcysC+cr). Reference GFR (mGFR) was determined using a non-isotopic iohexol plasma disappearance technique over 4h. Performance of each equation to mGFR was assessed by calculating bias, % bias, precision and accuracy for the total population, and according to age, sex, kidney disease, diabetes, obesity and c-reactive protein.

RESULTS

Data were available for 542 participants (38% men, mean [sd] age 45 [14] years). Bias was significantly greater for eGFRcysC (15.0mL/min/1.73m²; 95% CI 13.3-16.4, p<0.001) and eGFRcysC+cr (10.3; 8.8-11.5, p<0.001) compared to eGFRcr (5.4; 3.0-7.2). Accuracy was lower for eGFRcysC (80.3%; 76.7-83.5, p<0.001) but not for eGFRcysC+cr (91.9; 89.3-94.0, p=0.29) compared to eGFRcr (90.0; 87.2-92.4). Precision was comparable for all equations. The performance of eGFRcysC deteriorated across increasing levels of c-reactive protein.

CONCLUSION

Cystatin C based eGFR equations may not perform well in populations with high levels of chronic inflammation. CKD-EPI eGFR based on serum creatinine remains the preferred equation in Indigenous Australians.

The new Asian modified CKD-EPI equation leads to more accurate GFR estimation in Chinese patients with CKD

OBJECTIVE

To verify whether the new Asian modified CKD-EPI equation improved the performance of original one in determining GFR in Chinese patients with CKD.

METHOD

A well-designed paired cohort was set up. Measured GFR (mGFR) was the result of ^99mTc-diethylene triamine pentaacetic acid (^99mTc-DTPA) dual plasma sample clearance method. The estimated GFR (eGFR) was the result of the CKD-EPI equation (eGFR1) and the new Asian modified CKD-EPI equation (eGFR2). The comparisons were performed to evaluate the superiority of the eGFR2 in bias, accuracy, precision, concordance correlation coefficient and the slope of regression equation and measure agreement.

RESULTS

A total of 195 patients were enrolled and analyzed. The new Asian modified CKD-EPI equation improved the performance of the original one in bias and accuracy. However, nearly identical performance was observed in the respect of precision, concordance correlation coefficient, slope of eGFR against mGFR and 95 % limit of agreement. In the subgroup of GFR < 60 mL min^-1/1.73 m², the bias of eGFR1 was less than eGFR2 but they have comparable precision and accuracy. In the subgroup of GFR > 60 mL min^-1/1.73 m², eGFR2 performed better than eGFR1 in terms of bias and accuracy.

CONCLUSION

The new Asian modified CKD-EPI equation can lead to more accurate GFR estimation in Chinese patients with CKD in general practice, especially in the higher GFR group.

The new Asian modified CKD-EPI equation leads to more accurate GFR estimation in Chinese patients with CKD

OBJECTIVE

To verify whether the new Asian modified CKD-EPI equation improved the performance of original one in determining GFR in Chinese patients with CKD.

METHOD

A well-designed paired cohort was set up. Measured GFR (mGFR) was the result of ^99mTc-diethylene triamine pentaacetic acid (^99mTc-DTPA) dual plasma sample clearance method. The estimated GFR (eGFR) was the result of the CKD-EPI equation (eGFR1) and the new Asian modified CKD-EPI equation (eGFR2). The comparisons were performed to evaluate the superiority of the eGFR2 in bias, accuracy, precision, concordance correlation coefficient and the slope of regression equation and measure agreement.

RESULTS

A total of 195 patients were enrolled and analyzed. The new Asian modified CKD-EPI equation improved the performance of the original one in bias and accuracy. However, nearly identical performance was observed in the respect of precision, concordance correlation coefficient, slope of eGFR against mGFR and 95 % limit of agreement. In the subgroup of GFR < 60 mL min^-1/1.73 m², the bias of eGFR1 was less than eGFR2 but they have comparable precision and accuracy. In the subgroup of GFR > 60 mL min^-1/1.73 m², eGFR2 performed better than eGFR1 in terms of bias and accuracy.

CONCLUSION

The new Asian modified CKD-EPI equation can lead to more accurate GFR estimation in Chinese patients with CKD in general practice, especially in the higher GFR group.

Methodology used in studies reporting chronic kidney disease prevalence: a systematic literature review

Background

Many publications report the prevalence of chronic kidney disease (CKD) in the general population. Comparisons across studies are hampered as CKD prevalence estimations are influenced by study population characteristics and laboratory methods.

Methods

For this systematic review, two researchers independently searched PubMed, MEDLINE and EMBASE to identify all original research articles that were published between 1 January 2003 and 1 November 2014 reporting the prevalence of CKD in the European adult general population. Data on study methodology and reporting of CKD prevalence results were independently extracted by two researchers.

Results

We identified 82 eligible publications and included 48 publications of individual studies for the data extraction. There was considerable variation in population sample selection. The majority of studies did not report the sampling frame used, and the response ranged from 10 to 87%. With regard to the assessment of kidney function, 67% used a Jaffe assay, whereas 13% used the enzymatic assay for creatinine determination. Isotope dilution mass spectrometry calibration was used in 29%. The CKD-EPI (52%) and MDRD (75%) equations were most often used to estimate glomerular filtration rate (GFR). CKD was defined as estimated GFR (eGFR) <60 mL/min/1.73 m² in 92% of studies. Urinary markers of CKD were assessed in 60% of the studies. CKD prevalence was reported by sex and age strata in 54 and 50% of the studies, respectively. In publications with a primary objective of reporting CKD prevalence, 39% reported a 95% confidence interval.

Conclusions

The findings from this systematic review showed considerable variation in methods for sampling the general population and assessment of kidney function across studies reporting CKD prevalence. These results are utilized to provide recommendations to help optimize both the design and the reporting of future CKD prevalence studies, which will enhance comparability of study results.

Clinical implications of the CKD epidemiology collaboration (CKD-EPI) equation compared with the modification of diet in renal disease (MDRD) study equation for the estimation of renal dysfunction in patients with cardiovascular disease

The CKD-EPI equation is more accurate than the MDRD equation in the general population. We performed this study to establish whether chronic kidney disease (CKD) is commonly recognized by clinicians and whether the CKD-EPI equation improves prognosis estimation in patients with chronic cardiovascular disease (CVD). We analyzed data on 12394 CVD patients consecutively examined at the Cardiovascular Center of Trieste (Italy) between November 2009 and October 2013. The outcomes were all-cause death and a composite outcome of death/hospitalization for CV events (D+cvH). CKD-EPI formula reclassified 1786 (14.4 %) patients between KDIGO categories compared to the MDRD: 2.3 % (n = 280) placed in a lower risk and 12.1 % (n = 1506) into a higher risk group. CKD, defined as eGFR-CKD-EPI formula <60 ml/min, was present in 3083 patients (24.9 %) but not recognized by clinicians in 1946 (63.1 % of patients with CKD). The lack of recognition of CKD was inversely proportional to the KDIGO class for both equations. There were 986 deaths and 2726 D+cvH during 24 months follow-up. The incidence of death and D+cvH was about twice as high in patients with unrecognized CKD than in those with normal renal function (31 % vs. 17.1 %, aHR: 1.35, 95 % CI: 1.15 to 1.60), even in those patients with eGFR-MDRD >60 but eGFR-CKD-EPI formula <60 (31.1 % vs 17.1 %, p < 0.001). CKD-EPI equation provides more accurate risk stratification than MDRD equation in patients with CVD. CKD was unrecognized in nearly two-thirds of these patients but clinical outcomes were similar in those for patients with recognized CKD.

Glomerular filtration rate measured by (99m) Tc-DTPA renal dynamic imaging is significantly lower than that estimated by the CKD-EPI equation in horseshoe kidney patients

AIM

Gate's glomerular filtration rate (gGFR) measured by (99m) Tc-DTPA renal dynamic imaging and estimated GFR (eGFR) estimated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation are two indexes used to evaluate renal function. However, little is known about whether gGFR can be used to accurately assess renal function in horseshoe kidney (HSK) patients with renal fusion anomalies.

METHODS

Nineteen HSK patients (HSK group) diagnosed by renal imaging and 38 CKD patients with "normal kidney shape" (non-HSK group) matched to the HSK patients in terms of gender, age and biochemical indicators at Chinese PLA General Hospital were enrolled in this study. Gender, age, serum total protein (TP), albumin (ALB), blood urea nitrogen (BUN), serum creatinine (Scr), gGFR and eGFR were recorded and analyzed using χ(2) test, t-test, and Wilcoxon test which was presented as median(IQR).

RESULTS

(1) There were no significant differences in gender, age, TP, ALB, BUN, Scr, or eGFR between these two groups. (2) In HSK patients, the renogram showed abnormal renal axis with the lower poles orientated medially. The timed uptake curve showed that the isotope excretion in the HSK group was slower than that in the non-HSK group. (3) For all HSK patients, gGFR was significantly lower than eGFR (range -12.52 mL/min per 1.73m(2) to -93.18 mL/min per 1.73m(2) ). There was no significant difference in eGFR between the HSK [96.42 (36.02) mL/min per 1.73 m(2) ] and non-HSK groups [94.46 (33.00) mL/min per 1.73 m(2) ]. The gGFR of the HSK group [41.18 (16.60) mL/min per 1.73m(2) ] was much lower than that of the non-HSK group [86.42(26.40) mL/min per 1.73m(2) , P < 0.001] and the eGFR of the HSK group (P < 0.001). The gGFR and eGFR of the non-HSK group were not significantly different.

CONCLUSION

gGFR measured by (99m) Tc-DTPA renal dynamic imaging is significantly lower than eGFR estimated by the CKD-EPI equation, which indicates that isotope renogram cannot accurately evaluate the GFR of HSK patients.

Hyperfiltration in Indigenous Australians with and without diabetes

BACKGROUND

Hyperfiltration (HF) has been linked to the development of diabetic kidney disease (DKD), but the causative or predictive role of HF in the pathogenesis of DKD still remains unclear. To date, there have been no studies of HF in Indigenous Australians, a population with high rates of both diabetes and end-stage kidney disease. We aimed to compare the characteristics and frequency of HF in Indigenous Australians with and without type 2 diabetes.

METHODS

Indigenous Australian participants, recruited across five pre-defined strata of health, diabetes status and kidney function, had a reference glomerular filtration rate (GFR) measured using plasma disappearance of iohexol [measured GFR(mGFR)] over 4 h. HF was defined in various ways: (i) mGFR > 144 mL/min/1.73 m(2), which is mGFR > 1.96 × SD above the mean of the mGFR in non-diabetic participants with normal albuminuria and normal renal function (mGFR > 90 mL/min/1.73 m(2)); (ii) age-corrected mGFR (>144 mL/min/1.73 m(2)) to account for the effect of ageing on GFR in subjects over 40 years of age with cut-off 1 mL/min/1.73 m(2) lower for every year; (iii) mGFR > 144 mL/min, without correction for body surface area or age, as well as (iv) mGFR > 125 mL/min/1.73 m(2), without adjustment for age.

RESULTS

A total of 383 Indigenous participants, 125 with and 258 without diabetes, with mGFR > 90 mL/min/1.73 m(2) were studied. The proportion of participants with HF was 7% using mGFR > 144 mL/min/1.73 m(2), 11% using the age-adjusted definition, 19% using mGFR > 144 mL/min and 27% using mGFR > 125 mL/min/1.73 m(2). Diabetes was more common in participants with HF (40-74%) compared with normofiltering participants (28-31%), regardless of the definition of HF.

CONCLUSIONS

HF exists in Indigenous Australians with and without diabetes. A greater proportion of participants had diabetes in HF group compared with normofiltration group. Long-term follow-up of this cohort is necessary to determine if HF plays a role in the development of DKD and non-DKD.

Association between the body mass index and chronic kidney disease in men and women. A population-based study from Israel

BACKGROUND

Any association between the body mass index (BMI) and chronic kidney disease (CKD) has so far proved inconclusive. Most studies have estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease (MDRD) equation. This has recently been replaced by the more accurate Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation.

METHODS

In a cross-sectional study, data from a screening centre in Israel, n = 21880 (32% women) were used to assess the prevalence of CKD defined as eGFR < 60 mL/min/1.73 m(2) in relation to BMI categories. The CKD-EPI equation was used to assess the eGFR.

RESULTS

CKD was found in 167 men and 45 women. Subjects with a BMI of 25-29.9 kg/m(2), compared with those with a BMI of <25 kg/m(2), had an odds ratio (OR; 95% confidence intervals) for CKD of 1.8 (1.2-2.7) and 3.4 (1.5-7.7) for men and women, respectively. Subjects with a BMI of 30-35 kg/m(2) had an OR of 2.5 (1.6-4.0) and 4.5 (1.7-11.7) for men and women, respectively. In comparable data, for subjects with a BMI > 35 kg/m(2) the OR was 2.7 (1.3-5.5) and 15.4 (6.4-36.7) for men and women, respectively. After multivariate adjustment for age, hypertension and diabetes mellitus, no association was found in men yet it persisted for women. This correlation in women, between the BMI and CKD, was attributed to the subcategory of severely obese women with a BMI of >35 kg/m(2).

CONCLUSIONS

Our study is the first to suggest that morbid obesity may be an independent factor related to CKD in women.

Estimation of glomerular filtration rate to adjust vancomycin dosage in critically ill patients: superiority of the Chronic Kidney Disease Epidemiology Collaboration equation?

The purpose of this study was to determine the best estimate of glomerular filtration rate (GFR) to adjust vancomycin (VAN) dosage in critically ill patients. Seventy-eight adult intensive care unit patients received a 15 mg/kg loading dose of VAN plus a 30 mg/kg/day continuous infusion. Steady-state concentration was measured 48 hours later and the dose was adjusted to obtain a target concentration ranging from 20 to 25 mg/l. GFR was estimated by measured creatinine clearance (CLCR), Cockcroft, Modification of Diet in Renal Disease and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. The required dose providing the target concentration was 36±17 mg/kg/day. The first dosage had to be increased in 51% of all patients and in 84% of trauma patients (highest GFR), but had to be decreased in 17% of patients. The closest relationship between clearances of vancomycin was observed with CKD-EPI to GFR. The correlation between clearances of vancomycin and measured CLCR was significant but was rather poor with Cockcroft and Modification of Diet in Renal Disease equation. On the Bland and Altman plots, measured CLCR provided a lower bias but a larger confidence interval and a weaker precision than CKD-EPI. For VAN dose adjustments in intensive care unit patients, Cockcroft formula and Modification of Diet in Renal Disease should be used with caution. In clinical practice, the physician does not have at their disposal the patient's measured CLCR when prescribing. The CKD-EPI appears to be the best predictor of clearances of vancomycin for calculation of a therapeutic VAN regimen.

Applicability of chronic kidney disease epidemiology collaboration equations in a Chinese population

BACKGROUND

Accurate estimated glomerular filtration rates (eGFR) is an important step in the diagnosis of chronic kidney disease (CKD). The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, based on creatinine alone (eGFRcr), was developed to improve on the Modification of Diet in Renal Disease equation, in particular by addressing the systematic underestimation of high GFR. Whether the CKD-EPI equation, based on cystatin C alone (eGFRcys), or the combined creatinine-cystatin C CKD-EPI equation (eGFRcr-cys C), actually perform better than the CKD-EPI equation based on creatinine (eGFRcr) remains unknown, especially in Asians including Chinese populations, where eGFR equations may overestimate true GFR.

METHODS

A standard dual plasma sampling method (DPSM) of estimating (99m)Tc-diethylene triamine penta-acetic acid clearance was used to determine the reference or measured GFR (mGFR). Linear regression analysis, Bland-Altman analysis, bias, absolute bias and accuracy (P30) were used to compare the performance of the combined creatinine-cystatin C equation (eGFRcr-cys) and equations based on each marker alone (eGFRcr and eGFRcys) in Chinese subjects, including both patients with CKD and healthy individuals.

RESULTS

We enrolled 617 Chinese participants (49.11% female, 47.11 ± 17.25 years old), with a mean mGFR of 73.80 ± 37.55 mL/min/1.73 m(2). The predictive abilities (r), the accuracy (P15, P30, P50), bias and absolute bias of the eGFRcr-cys equation were superior to eGFRcr equation and the eGFRcys equation in overall samples. Bland-Altman analysis also demonstrated a consistent result. When compared in subgroups, the accuracy (P30) of all three equations exceeded 90% at mGFR ≥90 mL/min/1.73m(2); the eGFRcr-cys equation had the highest accuracy (P30: 95.56%). At mGFR 60-89 mL/min/1.73 m(2), the accuracies (P30) of the eGFRcr-cys and eGFRcr equations exceeded the acceptable level (≥70%), and there was no significant difference between them (P = 0.58). At mGFR <60 mL/min/1.73 m(2), the accuracy (P30) of all three equations was below 70%, but the eGFRcr-cys equation had the greatest precision.

CONCLUSIONS

The performances of the eGFRcr-cys and eGFRcr equations were similar to superior to that of the eGFRcys equation at higher GFR levels in an Asian population, especially in normal and mild to moderate kidney disease. Further improvement is needed for these equations at GFR <60 mL/min per 1.73 m(2).

Determinants and burden of chronic kidney disease in the population-based CoLaus study: a cross-sectional analysis

BACKGROUND

Chronic kidney disease (CKD) represents an increasing health burden. We present the population-based prevalence of CKD and compare the CKD Epidemiology collaboration (CKD-EPI) and modification of diet in renal disease (MDRD) equations to estimate the glomerular filtration rate, using the revised CKD classification with three albuminuria classes. We also explore factors associated with CKD.

METHODS

The Swiss population-based, cross-sectional CoLaus study conducted in Lausanne (2003-2006) included 2810 men and 3111 women aged 35-75. CKD prevalence was assessed using CKD-EPI and MDRD equations and albuminuria estimated by the albumin-to-creatinine ratio in spot morning urine. Multivariate logistic regression was used to analyse determinants of CKD.

RESULTS

Prevalence [95% confidence interval (CI)] of all stages CKD was 10.0% (9.2-10.8%) with CKD-EPI and 13.8% (12.9-14.6%) with MDRD. Using the revised CKD classification, the prevalence of low-, medium-, high- and very high-risk groups was 90.0, 8.46, 1.18 and 0.35% with CKD-EPI, respectively. With MDRD, the corresponding values were 86.24, 11.86, 1.55 and 0.35%. Using the revised classification, CKD-EPI systematically reclassified people in a lower risk category than MDRD. Age and obesity were more strongly associated with CKD in men [odds ratio (95% CI): 2.23(1.95; 2.56) per 10 years and 3.05(2.08;4.47), respectively] than in women [1.46 (1.29; 1.65) and 1.78 (1.30;2.44), respectively]. Hypertension, type 2 diabetes, serum homocysteine and uric acid were positively independently associated with CKD in men and women.

CONCLUSIONS

One in 10 adults suffers from CKD in the population of Lausanne. CKD-EPI systematically reclassifies people in a lower CKD risk category than MDRD. Serum homocysteine and uric acid levels are associated with CKD independently of classical risk factors such as age, hypertension and diabetes.