Is the Chronic Kidney Disease Epidemiology Collaboration creatinine-cystatin C equation useful for glomerular filtration rate estimation in the elderly?

Utility of cystatin C and serum creatinine-based glomerular filtration rate equations in predicting vancomycin clearance: A population pharmacokinetics analysis in elderly Chinese patients

Renal function is an important factor affecting the pharmacokinetics of vancomycin. The renal function in elderly patients gradually decreases with age. An accurate estimated glomerular filtration rate (GFR) is essential in drug dosing. The study aimed to determine the most appropriate renal function estimation equations to describe vancomycin pharmacokinetics in elderly patients using population pharmacokinetic analysis. Data were obtained retrospectively from elderly patients aged ≥65 years who received vancomycin for infection from September 2016 to January 2022. Renal function was estimated using the Cockcroft-Gault equation (CG), Modification of Diet in Renal Disease equation (MDRD), three Chronic Kidney Disease Epidemiology Collaboration equations (CKD-EPIcys-scr , CKD-EPIscr , and CKD-EPIcys ) and two Berlin Initiative Study equations (BIS-1 and BIS-2). The CKD-EPIcys-scr and BIS-2 equations were based on cystatin C (Cys C) and serum creatinine (Scr). The others were based on Cys C or Scr. A nonlinear mixed effects model (NONMEM) was used to develop the population pharmacokinetic model. A total of 471 serum concentrations from 313 elderly patients were used to develop the population pharmacokinetic model. Weight and GFR were identified as significant covariates affecting the pharmacokinetics of vancomycin. Cys C and Scr-based GFR (CKD-EPIcys-scr and BIS-2) yielded significant improvement performance compared with the other equations in model building. The interindividual variability of CL was reduced from 49.4% to 23.6% and 49.4% to 23.7% in CKD-EPIcys-scr and BIS-2 based models, respectively. However, greater interindividual variabilities of CL (from 26.6% to 29.0%) were represented in the other five models which were based on either Cys C or Scr. The GFR estimated by EPIcys-scr and BIS-2 equations and vancomycin CL exhibited a good correlation (r = 0.834 and 0.833). In the external validation with 124 serum concentrations, the predictive performances of the CKD-EPIcys-scr and BIS-2 based models (the mean relative prediction errors were less than 1%, the mean relative absolute prediction errors were about 23%) were also superior to the other five models (the mean relative prediction errors were about 2%, the mean relative absolute prediction errors were greater than 25%) which are based on either Cys C or Scr. In this study, we determined that the equation used to estimate GFR can affect the population pharmacokinetic model fitting result. Population pharmacokinetics model with CKD-EPIcys-scr or BIS-2 can be used to optimize vancomycin dosage in elderly Chinese patients.

Comparison of glomerular filtration rate estimating equations in older adults: A systematic review and meta-analysis

BACKGROUND

Debates persist regarding the performance of existing glomerular filtration rate (GFR) estimating equations in older individuals. We performed this meta-analysis to assess the accuracy and bias of six commonly used equations, including the Chronic Kidney Disease Epidemiology Collaboration creatinine equation (CKD-EPICr) and its combination with cystatin C (CKD-EPICr-Cys), with the corresponding pair of the Berlin Initiative Study equations (BIS1 and BIS2) and the Full Age Spectrum equations (FASCr and FASCr-Cys).

METHODS

PubMed and the Cochrane Library were searched for studies comparing estimated GFR (eGFR) with measured GFR (mGFR). We analyzed the difference in P30 and bias among the six equations and investigated subgroups based on the area (Asian and non-Asian), mean age (60-74 years and ≥75 years), and levels of mean mGFR (<45 mL/min/1.73m2 and ≥45 mL/min/1.73m2).

RESULTS

27 studies with 18,112 participants were included, all reporting P30 and bias. BIS1 and FASCr exhibited significantly higher P30 than CKD-EPICr. While no significant differences were observed between FASCr and BIS1, or among the three combined equations in terms of either P30 or bias. Subgroup analyses revealed FASCr and FASCr-Cys achieved better results in most situations. However, in the subgroup of mGFR<45 mL/min/1.73m2, CKD-EPICr-Cys had relatively higher P30 and significantly smaller bias.

CONCLUSIONS

Overall, BIS and FAS provided relatively more accurate estimates of GFR than CKD-EPI in older adults. FASCr and FASCr-Cys may be better suited for various conditions, while CKD-EPICr-Cys would be a better option for older individuals with impaired renal function.

Validation of the European Kidney Function Consortium Equation in Chinese Adult Population: An Equation Standing on the Shoulders of Predecessors

BACKGROUND

Equations based on serum creatinine (SCr) have been extensively applied to estimate glomerular filtration rate (GFR), but their performance is debatable. In 2021, the European Kidney Function Consortium (EKFC) published one novel SCr-based formula, which combined the feature of Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and full age spectrum (FAS) equations, but its potential applications remain unknown. We seek to assess the appropriateness of the three equations in Chinese adults.

METHODS

A total of 3,692 participants (median age, 54 years) were included. Reference GFR (rGFR) was measured by the 99mTc-DTPA renal dynamic imaging method. Estimated GFR (eGFR) was calculated by the CKD-EPI, FAS, and EKFC equations. Correlation coefficients and Bland-Altman analysis were adopted to evaluate their validity. The performance was assessed in subgroups according to age, sex, rGFR, and SCr, considering the bias, accuracy, and precision.

RESULTS

The average rGFR was 74.2 mL/min/1.73 m2. eGFR by EKFC showed a relatively stronger correlation with rGFR (R = 0.749) and a larger area under the receiver operating characteristic curve (0.902). EKFC was significantly less biased and exhibited the highest P30 in the entire population (bias = 3.61, P30 = 73.3%). It also performed well in all analyzed subgroups, especially in participants with normal or slightly impaired renal function (rGFR≥60 mL/min/1.73 m2), and low SCr.

CONCLUSIONS

Compared to the other two SCr-based formulas, EKFC performed better in the Chinese. Thus, it might serve as a good alternative, until a more suitable formula is developed for the Chinese population.

Glomerular filtration rate by different measures and albuminuria are associated with risk of frailty: the Rugao Longitudinal Ageing Study

BACKGROUND AND AIM

A decreased estimated glomerular filtration rate (eGFR) is associated with frailty, but the association between kidney function and frailty using multidimensional assessments has not been entirely examined. We aimed to investigate whether albuminuria and the eGFR using different biomarkers were associated with frailty.

METHODS

A total of 1830 older adults were included. Kidney function was assessed by the eGFR (based on combined creatinine-cystatin C [eGFR_cr-cys]) and β₂-microglobulin [eGFR_B2M]) and urine albumin-creatinine ratio (UACR). Frailty was measured by the Fried phenotype (FP) and frailty index (FI). Logistic regression models were used to investigate cross-sectional and longitudinal associations of baseline kidney measures with prevalent and incident frailty.

RESULTS

At baseline, kidney function was associated with prevalent frailty. During the 2-year follow-up, a decreased eGFR (per 10 units) was associated with an increased risk of incident frailty using the FP (eGFR_cr-cys: OR 1.18, 95% CI 1.03-1.35; eGFR_B2M: OR 1.14, 95% CI 1.02-1.29, respectively) and FI (eGFR_B2M: OR 1.18, 95% CI 1.04-1.65). An increased logUACR was associated with a higher risk of incident frailty using the FP (OR 1.18, 95% CI 1.03-1.35). Additionally, individuals with chronic kidney disease (CKD) had a higher risk of incident frailty using the FP (eGFR_cr-cys: OR 2.13, 95% CI 1.28-3.47; eGFR_B2M: OR 1.58, 95% CI 1.10-2.29, respectively) and FI (eGFR_cr-cys: OR 1.97, 95% CI 1.15-3.32; eGFR_B2M: OR 1.51, 95% CI 1.03-2.24, respectively).

CONCLUSION

Kidney function decline and CKD were associated with an increased risk of prevalent and incident frailty in older adults. Physicians should pay more attention to monitoring frailty status in older adults with CKD, even in those with kidney function decline.

Comparison of Creatinine and Cystatin C to Estimate Renal Function in Geriatric and Frail Patients

The aim of this study was to compare estimated glomerular filtration rate (eGFR) with creatinine (eGFRcrea) and cystatin C (eGFRcys) in geriatric and frail patients. A retrospective, cross-sectional study was performed at a geriatric clinic in Stockholm (n = 95). The revised Lund−Malmö equation was used to calculate eGFRcrea and the Caucasian-Asian-Pediatric-Adult (CAPA) equation was used for eGFRcys. The absolute mean percentage difference between eGFRcrea and eGFRcys was used as a surrogate measure for accuracy in eGFR. Other outcome measures were consistency expressed in Lin’s concordance correlation coefficient and the proportion of consistent staging of renal failure. Subgroup analyses were performed with regard to frailty (according to Clinical Frailty Scale) and age. eGFRcys estimated lower GFR than eGFRcrea across the entire study population as well as in all subgroups (p < 0.05). Difference between the estimates increased with increasing frailty (r2 = 0.15, p < 0.01), but was not significantly affected by age (r2 = 0.004, p = 0.55). In conclusion, eGFRcys was significantly lower compared to eGFRcrea in geriatric and frail patients. Moreover, frailty had greater impact than age on the accuracy of eGFR. However, this study cannot determine if any of the estimates are preferable over the other in this patient group.

The Link Between Conventional and Novel Anti-Cancer Therapeutics with Thrombotic Microangiopathy

BACKGROUND

Kidney disease associated with cancer and anti-cancer therapies has been increasingly recognized in the field of onco-nephrology. In particular, drug-induced nephrotoxicity has important implications since most chemotherapeutic agents have a nephrotoxic potential. Also, standard creatinine clearance methods used for the measurement of kidney function have been questioned in cancer patients due to factors like low muscle mass and poor nutritional status. Overestimations of the glomerular filtration rate, not only can increase the nephrotoxic potential of different agents, but also further limit the use of first-line therapies.

OBJECTIVE

This review covers specifically the drug-induced thrombotic microangiopathy and its two pathophysiologic mechanisms which include immune or idiosyncratic reactions, and non-immune or dose-dependent ones.

CONCLUSION

As novel cancer therapies are developed, it is paramount to pursue a better understanding of conventional and novel chemotherapeutic agents and their role in kidney disease.

Estimation of renal function by three CKD-EPI equations in Chinese HIV/AIDS patients: A STROBE-compliant article

Assessing renal function accurately is important for human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) patients. Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) recommended three equations to calculate estimated glomerular filtration rate (eGFR). There is evidence that eGFR based on the combination of serum creatinine and cystatin C is the most accurate of the three equations. But there is limited data on the comparison of three CKD-EPI equations in Chinese HIV/AIDS patients. The aim of our study was to compare the three CKD-EPI equations in Chinese HIV/AIDS population and assess renal function.Cross-sectional, single center, prospective study.One hundred seventy two Chinese adult HIV/AIDS patients were enrolled, including 145 (84.3%) males and 27 (15.7%) females. Mean age was 40(±12) years old. Overall mean eGFR based on serum creatinine, cystatin C and the combination of the 2 markers was 112.6(±19.0) mL/min/1.73 m2, 92.0(±24.2)mL/min/1.73 m2, and 101.7(±21.8)mL/min/1.73 m2, respectively (P = .000). The eGFR calculated by serum creatinine alone is higher than eGFR calculated by combination of serum creatinine and cystatin C, and eGFR calculated by cystatin C individual is lower than eGFR calculated by combination of the 2 markers.Of the 3 CKD-EPI equations, the CKD-EPIscr-cys equation may have the most accuracy in evaluating renal function in Chinese HIV/AIDS patients while the CKD-EPIscr equation may overestimate renal function and the CKD-EPIcys equation may underestimate renal function.

Comparison of 99mTc-DTPA and serum creatinine, cystatin C in detection of glomerular filtration rate: a retrospective clinical data analysis of 744 Chinese subjects

BACKGROUND

To compare the accuracy of various equations for estimating glomerular filtration rate.

METHODS

Chronic kidney disease was classified by Tc-DTPA scintigraphy (reference glomerular filtration rate), estimating glomerular filtration rate was estimated using various formulas. The similarity to reference glomerular filtration rate decide the accuracy of estimating glomerular filtration rate.

RESULTS

Overall, the Fengscr-cys equation had significantly higher accuracy and correct proportion in chronic kidney disease stage classification than other equations. The subgroup analysis showed that Fengscr-cys equation was slightly more precise than other equations both in the male and female patients. Moreover, in patients older than 60 years or whose reference glomerular filtration rate was above 60 ml/min, Fengscr-cys equation also showed better accuracy.

CONCLUSION

Our data suggest that estimating glomerular filtration rate equations evaluated by serum cystatin C were better than serum creatinine-based equations, estimating glomerular filtration rate equations evaluated by both serum creatinine and cystatin C were better than those evaluated by serum creatinine or cystatin C alone. Among all enrolled equations, Fengscr-cys equation might be the best one to evaluate glomerular filtration rate in general Chinese paticipants.

Clinical factors increasing discrepancies of renal function assessment with MDRD and Cockcroft-Gault equations in old individuals

ABSTRACT

In a daily clinical practice, glomerular filtration rate (GFR) is still estimated on the basis of short MDRD formula, whereas medications' Summaries of Product Characteristics suggest that GFR used for the dosage adjustment should be estimated based on the Cockcroft-Gault (C-G) equation. The aim of the study was to compare eGFR values calculated on the basis of short and full MDRD and C-G equations in PolSenior study participants with decreased eGFR.

METHODS

We have assessed differences in the estimation of GFR between short and full MDRD, as well as C-G formula, all equations utilizing non-isotope-dilution mass spectrometry-calibrated measurements of serum creatinine, in the community-based population of 760 persons aged 65 years or above (mean age 82 ± 8 years) with estimated GFR < 60 ml/min/1.73 m2 (according to short MDRD). In addition, in our analysis, we have included the detailed characteristics of comorbidities and different aspects of mobility and functional performance.

RESULTS

The better concordance, precision, and accuracy with MDRD short formula were found for MDRDfull than C-G equation. In logistic regression analysis, female gender, activities in daily living (ADL) ≤ 4, and age > 80 years diminished, while visceral obesity improved accuracy (P30) of eGFR calculated according to C-G equation as compared to MDRDshort. Similar analysis did not found factors influencing P30 for MDRDfull equation.

CONCLUSIONS

In very old subjects, especially females, dependent patients and those with visceral obesity, estimation of GFR based on short MDRD formula should not be used interchangeably with Cockcroft-Gault equation for the medicines dose tailoring.

Estimation of the glomerular filtration rate in older individuals with serum creatinine-based equations: A systematic comparison between CKD-EPI and BIS1

AIM

CKD-EPIcr (Chronic Kidney Disease Epidemiology Collaboration creatinine) and BIS1 (Berlin Initiative Study) are two serum creatinine-based formulae for the estimation of glomerular filtration rate (GFR). However, their comparative accuracy in older people has not been well established. Our aim was to conduct a systematic comparative study of the accuracy of estimation of GFR in older people with these two formulae.

METHODS

We conducted a systematic search in Pubmed, EMBASE and Central databases on the validity of the CKD-EPIcr and BIS1 formulae in people aged 60 or more years. The search ranged from 2009 and 2012 for CKD-EPIcr and BIS1, respectively, until May 2017. The validity criterion for comparing the formulae was to have a P30 accuracy level equal to or greater than 80%.

RESULTS

Of 1295 identified studies, 16 met our inclusion criteria. Out of 16 studies reporting the accuracy of the CKD-EPIcr formula, only 5 (31.3%) had P30 scores ≥80% (mean P30 was 77.1 ± 7.711 range 55.5-91.7), and out of 9 studies on accuracy using the BIS1 formula, 6 (66.7%) were ≥80% (mean P30 was 83.88 ± 9.37, range 67.0-95.8).

CONCLUSION

Our results suggest that for the estimation of the GFR in older people, BIS1 formula may be more accurate than CKD-EPIcr.

CKD-EPI creatinine-cystatin C glomerular filtration rate estimation equation seems more suitable for Chinese patients with chronic kidney disease than other equations

BACKGROUND

The aim of this study was to identify the optimal equation that accurately estimates the glomerular filtration rate (GFR) and the chronic kidney disease (CKD) stage in the Chinese population.

METHODS

A total of 1296 Chinese patients aged 18-65 years old were enrolled in this study. The estimated GFRs (eGFRs) calculated separately by three Diet in Renal Disease (MDRD) equations and three Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations were compared with the reference GFR (rGFR) measured by the ⁹⁹Tc^m-DTPA renal dynamic imaging method.

RESULTS

By Bland-Altman analysis, eGFR_cys and eGFR_{scr_cys} performed similarly, showing the tightest limits of agreement among the six equations. They also achieved the first and second highest 30% and 50% accuracies. Using a combination of the serum creatinine and cystatin C levels (eGFR_{scr_cys}) could improve the bias (-0.3 for eGFR_{scr_cys}) of the equation and achieve the highest diagnostic accuracy for renal insufficiency (AUC₆₀, 0.953; P < 0.05, except for eGFR__MDRD). All equations predicted stage 3 CKD with moderate accuracy (49.7-51.4%) and stage 5 CKD with good accuracy (90.2-96.4%). For stage 1 CKD, eGFR_cys showed a higher percentage of misclassification than the other equations. All equations seemed to perform poorly at predicting stage 2 and 4 CKD, as compared to the other CKD stages. eGFR_{scr_cys} was the best-performing equation in terms of accurate classification of the CKD stage based on the overall performance (kappa value, 0.423).

CONCLUSION

For a Chinese population, the CKD-EPI_{scr_cys} equation seems more suitable for estimating the GFR than the other equations. Each equation had its own advantages in predicting different CKD stages.

Estimating glomerular filtration rate by serum creatinine or/and cystatin C equations: An analysis of multi-centre Chinese subjects

AIM

Various equations based on serum creatinine or/and cystatin C, required further validation in a Chinese population. We compared the performance of six Chinese equations (Mascr, Peiscr, Macys, Fengcys, Mascr-cys and Fengscr-cys) with the CKD-EPI equations in multi-centre Chinese subjects and evaluated their applicability in clinical practice.

METHODS

A total of 1522 adult patients from four different hospitals of China were enrolled in the study. (99m) Tc-DTPA renal dynamic imaging was used as the reference GFR (rGFR), and serum creatinine and cystatin C were measured by standardized assays. An optimal score system was implemented in the study.

RESULTS

The average rGFR of recruited subjects was 67.30±28.89 mL/min per 1.73m(2) . All estimated GFR (eGFR) correlated well with rGFR. In accordance with Bland-Altman analysis, the Fengscr-cys equations achieved optimal overall performance (score 14 vs 0-6), with least bias (median difference, -0.57 mL/min per 1.73m(2) ; median absolute difference, 8.83 mL/min per 1.73m(2) ), best precision (17.99 mL/min per 1.73m(2) ), highest accuracy (percentage of eGFR within 15%, 30% and 50% of the rGFR (P15 , P30 and P50 ; 49.7%, 78.7% and 91.8%, respectively); root-mean-square-error (RMSE, 16.28)). The Fengcys equation, a typical cystatin C based equation, was another well-behaved formula with an impressive performance. The Ma equations performed much poorer than the CKD-EPI equations. Consistent results can be observed in the GFR- /age- and sex-specific subgroups, while none equation yielded ideal accuracy in GFR<60 mL/min per 1.73 m(2) subgroup.

CONCLUSION

The Fengscr-cys equation appeared to achieve the best performance for GFR estimation in overall Chinese adult patients. However, further research is warranted to improve the accuracy of available equations in GFR less than 60 mL/min per 1.73 m(2) individuals.

Performance of the creatinine and cystatin C-based equations for estimation of GFR in Chinese patients with chronic kidney disease

BACKGROUND

Currently, creatinine- or cystatin C-based glomerular filtration rate (GFR) estimation equation has been recommended to assess GFR in CKD patients. However, it is still obscure whether those equations performed consistently outstandingly in Chinese population.

METHODS

The equations were validated in a population totaling 632 participants (mean age 61.6 ± 12.3 years). The estimated GFR (eGFR) calculated separately by six equations (C-MDRD, C_cys, C_scr-cys, CKD-EPI_scr, CKD-EPI_cys, and CKD-EPI_scr-cys equations) was compared with the reference GFR (rGFR) measured by the ^99mTc-DTPA renal dynamic imaging method. Participants were divided into age and rGFR specific subgroups.

RESULTS

CKD-EPI_scr-cys equation had a larger area under receiver operating characteristic curve (ROC^AUC) and relative higher sensitivity (79.8 %) and specificity (93 %) to diagnose CKD. CKD-EPI_scr-cys and CKD-EPI_cys equations appeared to be more accurate with higher proportion of eGFR within 30 % of rGFR (P ₃₀) value. Those two equations performed as well in older people as in the younger population. The CKD-EPI_scr-cys equation acquired the highest P ₃₀ (80.9 %) in subgroups with rGFR ≥60 mL/min/1.73 m², while the CKD-EPI_cys equation yielded the best performance in the rGFR <60 mL/min/1.73 m² subgroup.

CONCLUSION

CKD-EPI_scr-cys formula had better capability to accurately evaluate GFR in the participants CKD stages 1-2 in Chinese ethnic. The application of the cystatin C-based equations may be the optimal one for patients of moderately to severely injured GFR. Considering the accuracy in the entire range of participants less ideally, the additional of the Chinese racial factor is assumed to be essential.

Performance of cystatin C- and creatinine-based estimated glomerular filtration rate equations depends on patient characteristics

BACKGROUND

The Kidney Disease Improving Global Outcomes (KDIGO) guideline recommends use of a cystatin C-based estimated glomerular filtration rate (eGFR) to confirm creatinine-based eGFR between 45 and 59 mL · min(-1) · (1.73 m(2))(-1). Prior studies have demonstrated that comorbidities such as solid-organ transplant strongly influence the relationship between measured GFR, creatinine, and cystatin C. Our objective was to evaluate the performance of cystatin C-based eGFR equations compared with creatinine-based eGFR and measured GFR across different clinical presentations.

METHODS

We compared the performance of the CKD-EPI 2009 creatinine-based estimated GFR equation (eGFRCr) and the newer CKD-EPI 2012 cystatin C-based equations (eGFRCys and eGFRCr-Cys) with measured GFR (iothalamate renal clearance) across defined patient populations. Patients (n = 1652) were categorized as transplant recipients (n = 568 kidney; n = 319 other organ), known chronic kidney disease (CKD) patients (n = 618), or potential kidney donors (n = 147).

RESULTS

eGFRCr-Cys showed the most consistent performance across different clinical populations. Among potential kidney donors without CKD [stage 2 or higher; eGFR >60 mL · min(-1) · (1.73 m(2))(-1)], eGFRCys and eGFRCr-Cys demonstrated significantly less bias than eGFRCr; however, all 3 equations substantially underestimated GFR when eGFR was <60 mL · min(-1) · (1.73 m(2))(-1). Among transplant recipients with CKD stage 3B or greater [eGFR <45 mL · min(-1) · (1.73 m(2))(-1)], eGFRCys was significantly more biased than eGFRCr. No clear differences in eGFR bias between equations were observed among known CKD patients regardless of eGFR range or in any patient group with a GFR between 45 and 59 mL · min(-1) · (1.73 m(2))(-1).

CONCLUSIONS

The performance of eGFR equations depends on patient characteristics that are readily apparent on presentation. Among the 3 CKD-EPI equations, eGFRCr-Cys performed most consistently across the studied patient populations.

A new modified CKD-EPI equation for Chinese patients with type 2 diabetes

Objective

To improve the performance of glomerular filtration rate (GFR) estimating equation in Chinese type 2 diabetic patients by modification of the CKD-EPI equation.

Design and patients

A total of 1196 subjects were enrolled. Measured GFR was calibrated to the dual plasma sample ^99mTc-DTPA-GFR. GFRs estimated by the re-expressed 4-variable MDRD equation, the CKD-EPI equation and the Asian modified CKD-EPI equation were compared in 351 diabetic/non-diabetic pairs. And a new modified CKD-EPI equation was reconstructed in a total of 589 type 2 diabetic patients.

Results

In terms of both precision and accuracy, GFR estimating equations all achieved better results in the non-diabetic cohort comparing with those in the type 2 diabetic cohort (30% accuracy, P≤0.01 for all comparisons). In the validation data set, the new modified equation showed less bias (median difference, 2.3 ml/min/1.73 m² for the new modified equation vs. ranged from −3.8 to −7.9 ml/min/1.73 m² for the other 3 equations [P<0.001 for all comparisons]), as was precision (IQR of the difference, 24.5 ml/min/1.73 m² vs. ranged from 27.3 to 30.7 ml/min/1.73 m²), leading to a greater accuracy (30% accuracy, 71.4% vs. 55.2% for the re-expressed 4 variable MDRD equation and 61.0% for the Asian modified CKD-EPI equation [P = 0.001 and P = 0.02]).

Conclusion

A new modified CKD-EPI equation for type 2 diabetic patients was developed and validated. The new modified equation improves the performance of GFR estimation.

Application of creatinine- and/or cystatin C-based glomerular filtration rate estimation equations in elderly Chinese

Background

No conventional creatinine- or cystatin C-based glomerular filtration rate (GFR) estimation equation performed consistently outstandingly in elderly Chinese in our previous studies. This research aimed to further evaluate the performance of some recently proposed estimation equations based on creatinine and cystatin C, alone or combined, in this specific population.

Materials and methods

The equations were validated in a population totaling 419 participants (median age 68 [range 60–94] years). The estimated GFR (eGFR) calculated separately by ten equations was compared with the reference GFR (rGFR) measured by the ^99mTc-DTPA renal dynamic imaging method.

Results

Median serum creatinine, cystatin C, and rGFR levels were 0.93 mg/L, 1.13 mg/L, and 74.20 mL/min/1.73 m², respectively. The Chinese population-developed creatinine- and cystatin C-based (Cscr-cys) equation yielded the least median absolute difference (8.81 vs range 9.53–16.32, P<0.05, vs the Chronic Kidney Disease Epidemiology Collaboration serum creatinine equation), the highest proportion of eGFR within 15% and 30% of rGFR (P₁₅ and P₃₀, 55.13 and 85.44, P<0.05 and P<0.01, vs the Chronic Kidney Disease Epidemiology Collaboration serum creatinine equation), and the lowest root mean square error (14.87 vs range 15.30–22.45) in the whole cohort. A substantial agreement of diagnostic consistency between eGFR and rGFR (with a kappa 0.61–0.80) was also observed with the Cscr-cys equation. Moreover, measures of performance in the Cscr-cys equation were consistent across normal to mildly injured GFR strata and individuals aged ≤80 years. Among all the Cscr-cys equations, the elderly Chinese-developed creatinine-based (CEscr) equation performed best in this specific population. Nevertheless, none of the equations achieved ideal manifestation in the moderately to severely GFR-injured group or in individuals aged ≥80 years.

Conclusion

The Cscr-cys equation appeared to be optimal in elderly Chinese among the investigated equations. If cystatin C is not available, the CEscr equation is an acceptable alternative. A multicenter study with abundant subjects to develop an apposite formula for elderly Chinese is assumed to be essential.

Improved glomerular filtration rate estimation using new equations combined with standardized cystatin C and creatinine in Chinese adult chronic kidney disease patients

OBJECTIVES

The newly developed glomerular filtration rate (GFR)-estimating equations developed by the CKD-EPI Collaboration and Feng et al. (2013) that are based on standardized serum cystatin C (ScysC), combined/not combined with serum creatinine (Scr), require further validation in China. We compared the performance of four new equations (CKD-EPIcys, CKD-EPIcr-cys, Fengcys, and Fengcr-cys equations) with the CKD-EPI creatinine equation (CKD-EPIcr) in adult Chinese chronic kidney disease (CKD) patients to clarify their clinical application.

DESIGN AND METHODS

GFR was measured using the dual plasma sampling (99m)Tc-DTPA method (mGFR) in 252 adult CKD patients enrolled from four centres. Scr and ScysC were measured by standardized assays in a central laboratory. Each equation's performance was assessed using bias, precision, accuracy, agreement, and correct classification of the CKD stage.

RESULTS

The measured GFR was 46 [25-83] mL/min per 1.73 m(2). The CKD-EPIcys, CKD-EPIcr-cys and Fengcys equations provided significantly higher accuracy (P15: 38.9%, 39.7%, and 38.9%) than the CKD-EPIcr equation (29.8%). The CKD-EPIcr-cys and Fengcr-cys equations presented higher precision (IQR of the difference, 16.4 and 17.3 mL/min per 1.73 m(2), respectively) and narrower acceptable limits in Bland-Altman analysis (56.6 and 50.8 mL/min per 1.73 m(2), respectively) than single marker-based equations. The CKD-EPIcr-cys equation achieved the highest overall correct proportion (61.5%) in classification of CKD stages.

CONCLUSIONS

Combining ScysC and Scr measurements for GFR estimation improves diagnostic performance. The Scr-ScysC equation showed better performance than equations based on either marker alone. The CKD-EPIcr-cys equation showed the best performance for GFR estimation in Chinese adult CKD patients.