Modification of the CKD epidemiology collaboration (CKD-EPI) equation for Japanese: accuracy and use for population estimates

(99m)Tc-DTPA renal dynamic imaging method may be unsuitable to be used as the reference method in investigating the validity of CDK-EPI equation for determining glomerular filtration rate

OBJECTIVE

To compare the measurements of glomerular filtration rate (GFR) determined by (99m)Tc-diethylene triamine pentaacetic acid ((99m)Tc-DTPA) renal dynamic imaging with those estimated by Chronic Kidney Disease Epidemiology Collaboration (CDK-EPI) equation and to identify a more accurate measurement of GFR of chronic kidney disease (CKD) patients in clinical practice.

METHODS

The GFR was determined simultaneously by 3 methods: (a) dual plasma sample clearance method (tGFR); (b) renal dynamic imaging method (dGFR); (c) CDK-EPI equation (eGFR). The tGFR was employed as the reference method. The correlation, regression, and limit of agreement of dGFR and eGFR were used to demonstrate the validity of the two methods. The comparison of bias, precision, and accuracy between dGFR and eGFR was analyzed to identify the most suitable method. The analysis of bias, precision and accuracy was repeated after stratifying patients by a measured tGFR cutpoint of 60 ml·min(-1)·(1.73 m(2))(-1).

RESULTS

A total of 149 patients were enrolled. Both dGFR and eGFR correlated well with tGFR and the regression equation of dGFR and eGFR against tGFR was respectively Y = -4.289+0.962X (r = 0.919; RMSE = 14.323 ml.min(-1). (1.73 m(2))(-1); P<0.001) and Y = 2.462+0.914X (r = 0.909; RMSE = 15.123 ml.min(-1). (1.73 m(2))(-1); P<0.001). In addition, Bland-Altman analysis showed preferable agreement between the two methods and the reference method. The comparison revealed that eGFR, compared with dGFR, showed better performance on bias and 50% accuracy and similar performance on other indexes in the whole cohort and the lower-GFR subgroup, whereas in the higher-GFR subgroup the difference of the two methods was not significant in all parameters.

CONCLUSIONS

Although both CDK-EPI equation and renal dynamic imaging can be used to determine the GFR of CKD patients, CDK-EPI equation is more accurate than renal dynamic imaging. As a result, (99m)Tc-DTPA renal dynamic imaging may be unsuitable to be used as the reference method in investigating the validity of CDK-EPI equation.

Comparison of estimating equations for the prediction of glomerular filtration rate in kidney donors before and after kidney donation

The aim of this study is to investigate the usefulness of the GFR-estimating equations to predict renal function in kidney donors before and after transplantation. We compared the performance of 24-hour-urine–based creatinine clearance (24 hr urine-CrCl), the Cockcroft-Gault formula (eGFR_CG), the Modification of Diet in Renal Disease equation (eGFR_MDRD), and the Chronic Kidney Disease Epidemiology Collaboration equation (eGFR_CKD-EPI) with technetium-diethylenetriaminepentaacetic acid (^99mTc-DTPA) clearance (mGFR) in 207 potential kidney donors and 108 uninephric donors. Before donation, eGFR_CKD-EPI showed minimal bias and did not show a significant difference from mGFR (P = 0.65, respectively) while 24 hr urine-CrCl and eGFR_MDRD significantly underestimated mGFR (P<0.001 for each). Precision and accuracy was highest in eGFR_CKD-EPI and this better performance was more dominant when renal function is higher than 90 mL·min⁻¹·1.73 m⁻². After kidney donation, eGFR_MDRD was superior to other equations in precision and accuracy in contrast to before donation. Within individual analysis, eGFR_MDRD showed better performance at post-donation compared to pre-donation, but eGFR_CKD-EPI and eGFR_CG showed inferior performance at post-donation. In conclusion, eGFR_CKD-EPI showed better performance compared to other equations before donation. In a uninephric donor, however, eGFR_MDRD is more appropriate for the estimation of renal function than eGFR_CKD-EPI.

Ethnic differences in creatinine kinetics in a New Zealand end-stage kidney disease cohort

BACKGROUND

Recent data have suggested that glomerular filtration rate (GFR) is better predicted in New Zealand (NZ) Māori and Pacific People using the equations for Black people that predict higher GFR for any given serum creatinine. We hypothesized that this might be due to a higher rate of creatinine generation in NZ Māori and Pacific People.

AIM

To compare creatinine kinetics between different ethnic groups in a cohort of NZ peritoneal dialysis patients.

METHODS

In this retrospective single-centre observational study, creatinine kinetics in 181 patients were determined from timed serum samples, peritoneal dialysate and urine collections between 1 October 2004 and 31 July 2011. Ethnicity was classified as Asian, NZ European, NZ Māori and Pacific People.

RESULTS

A total of 799 samples from 181 patients were analysed: 194 in Asians, 127 in NZ Europeans, 268 in NZ Māori, 207 in Pacific People. Pacific People had the highest serum creatinine and lean body mass, and the highest creatinine generation rate at 1349 mg/day, compared with 1049 for Asians, 1186 for NZ Europeans and 1094 for NZ Māori (P = 0.0001). After adjustment for confounding factors, Pacific People had a greater creatinine generation by 140 mg/day compared with NZ Europeans (P = 0.047).

CONCLUSION

Pacific People on peritoneal dialysis in NZ have higher serum creatinine, lean body mass and creatinine generation than other ethnic groups. This is consistent with previous observations that equations for predicting GFR in Black people may have increased accuracy in some Australasian non-White non-Asian populations.

Prediction of glomerular filtration rate in cancer patients by an equation for Japanese estimated glomerular filtration rate

BACKGROUND

Assessment of renal function is important for safe cancer chemotherapy, and eligibility criteria for clinical trials often include creatinine clearance. However, creatinine clearance overestimates glomerular filtration rate, and various new formulae have been proposed to estimate glomerular filtration rate. Because these were developed mostly in patients with chronic kidney disease, we evaluated their validity in cancer patients without kidney disease.

METHODS

Glomerular filtration rate was measured by inulin clearance in 45 Japanese cancer patients, and compared with creatinine clearance measured by 24-h urine collection as well as that estimated by the Cockcroft-Gault formula, Japanese estimated glomerular filtration rate developed in chronic kidney disease patients, the Modification of Diet in Renal Disease study equation and the Chronic Kidney Disease Epidemiology Collaboration equation. The Modification of Diet in Renal Disease study and Chronic Kidney Disease Epidemiology Collaboration equations were adjusted for the Japanese population by multiplying by 0.808 and 0.813, respectively.

RESULTS

The mean inulin clearance was 79.2 ± 18.7 ml/min/1.73 m(2). Bias values to estimate glomerular filtration rate for Japanese estimated glomerular filtration rate, the Cockcroft-Gault formula, creatinine clearance measured by 24-h urine collection, the 0.808 × Modification of Diet in Renal Disease study equation and the 0.813 × Chronic Kidney Disease Epidemiology Collaboration equation were 0.94, 9.75, 29.67, 5.26 and -0.92 ml/min/1.73 m(2), respectively. Precision (root-mean square error) was 14.7, 22.4, 39.8, 16.0 and 14.1 ml/min, respectively. Of the scatter plots of inulin clearance versus each estimation formula, the Japanese estimated glomerular filtration rate correlated most accurately with actual measured inulin clearance.

CONCLUSION

The Japanese estimated glomerular filtration rate and the 0.813 × Chronic Kidney Disease Epidemiology Collaboration equation estimated glomerular filtration rate with lower bias and higher precision than the other formulae. We therefore propose Japanese estimated glomerular filtration rate for the estimation of glomerular filtration rate in Japanese cancer patients.

Tolvaptan in patients with autosomal dominant polycystic kidney disease

BACKGROUND

The course of autosomal dominant polycystic kidney disease (ADPKD) is often associated with pain, hypertension, and kidney failure. Preclinical studies indicated that vasopressin V(2)-receptor antagonists inhibit cyst growth and slow the decline of kidney function.

METHODS

In this phase 3, multicenter, double-blind, placebo-controlled, 3-year trial, we randomly assigned 1445 patients, 18 to 50 years of age, who had ADPKD with a total kidney volume of 750 ml or more and an estimated creatinine clearance of 60 ml per minute or more, in a 2:1 ratio to receive tolvaptan, a V(2)-receptor antagonist, at the highest of three twice-daily dose regimens that the patient found tolerable, or placebo. The primary outcome was the annual rate of change in the total kidney volume. Sequential secondary end points included a composite of time to clinical progression (defined as worsening kidney function, kidney pain, hypertension, and albuminuria) and rate of kidney-function decline.

RESULTS

Over a 3-year period, the increase in total kidney volume in the tolvaptan group was 2.8% per year (95% confidence interval [CI], 2.5 to 3.1), versus 5.5% per year in the placebo group (95% CI, 5.1 to 6.0; P<0.001). The composite end point favored tolvaptan over placebo (44 vs. 50 events per 100 follow-up-years, P=0.01), with lower rates of worsening kidney function (2 vs. 5 events per 100 person-years of follow-up, P<0.001) and kidney pain (5 vs. 7 events per 100 person-years of follow-up, P=0.007). Tolvaptan was associated with a slower decline in kidney function (reciprocal of the serum creatinine level, -2.61 [mg per milliliter](-1) per year vs. -3.81 [mg per milliliter](-1) per year; P<0.001). There were fewer ADPKD-related adverse events in the tolvaptan group but more events related to aquaresis (excretion of electrolyte-free water) and hepatic adverse events unrelated to ADPKD, contributing to a higher discontinuation rate (23%, vs. 14% in the placebo group).

CONCLUSIONS

Tolvaptan, as compared with placebo, slowed the increase in total kidney volume and the decline in kidney function over a 3-year period in patients with ADPKD but was associated with a higher discontinuation rate, owing to adverse events. (Funded by Otsuka Pharmaceuticals and Otsuka Pharmaceutical Development and Commercialization; TEMPO 3:4 ClinicalTrials.gov number, NCT00428948.).

Trends in estimated kidney function: the FINRISK surveys

We evaluated the temporary trend in estimated glomerular filtration rate (eGFR) of subjects aged from 25 to 74 years between two cross-sectional population surveys in 2002 and in 2007. The mean eGFR across age-groups, the prevalences of eGFR categories, and the prevalence of chronic kidney disease (CKD) stage 3–5 defined by eGFR\60 mL/min/1.73 m2 were defined in sex- and age-specific groups using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Study equation. The eGFR decreased from year 2002 to 2007 across the age-groups in both genders. The prevalence of CKD stage 3–5 (eGFR\60 mL/min/1.73) increased in women from 1.8 to 3.1% (P=0.017), but not in men. In the combined analysis of both genders, CKD stage 3–5 was markedly more common in 2007 compared to 2002, with odds ratio (OR) 1.59 (95% confidence interval (CI) 1.22–2.08) remaining significant after adjusting the model for age, gender, study area, hypertension, obesity, prior cardiovascular disease, and diabetes mellitus, and being at lowest when only age, gender and waist circumference were included in the model (OR 1.34; 95% CI 1.02–1.76). To conclude, the mean eGFR decreased significantly during 2002–2007 in both sexes, and CKD stage 3–5 increased in women. This trend was concurrent with increases in mean waist circumference and in the prevalence of diabetes mellitus.

Estimated GFR and incident cardiovascular disease events in American Indians: the Strong Heart Study

BACKGROUND

In populations with high prevalences of diabetes and obesity, estimating glomerular filtration rate (GFR) by using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation may predict cardiovascular disease (CVD) risk better than by using the Modification of Diet in Renal Disease (MDRD) Study equation.

STUDY DESIGN

Longitudinal cohort study comparing the association of GFR estimated using either the CKD-EPI or MDRD Study equation with incident CVD outcomes.

SETTING & PARTICIPANTS

American Indians participating in the Strong Heart Study, a longitudinal population-based cohort with high prevalences of diabetes, CVD, and CKD.

PREDICTOR

Estimated GFR (eGFR) predicted using the CKD-EPI and MDRD Study equations.

OUTCOMES

Fatal and nonfatal cardiovascular events, consisting of coronary heart disease, stroke, and heart failure.

MEASUREMENTS

The association between eGFR and outcomes was explored in Cox proportional hazards models adjusted for traditional risk factors and albuminuria; the net reclassification index and integrated discrimination improvement were determined for the CKD-EPI versus MDRD Study equations.

RESULTS

In 4,549 participants, diabetes was present in 45%; CVD, in 7%; and stages 3-5 CKD, in 10%. During a median of 15 years, there were 1,280 cases of incident CVD, 929 cases of incident coronary heart disease, 305 cases of incident stroke, and 381 cases of incident heart failure. Reduced eGFR (<90 mL/min/1.73 m2) was associated with adverse events in most models. Compared with the MDRD Study equation, the CKD-EPI equation correctly reclassified 17.0% of 2,151 participants without incident CVD to a lower risk (higher eGFR) category and 1.3% (n=28) were reclassified incorrectly to a higher risk (lower eGFR) category.

LIMITATIONS

Single measurements of eGFR and albuminuria at study visits.

CONCLUSIONS

Although eGFR based on either equation had similar associations with incident CVD, coronary heart disease, stroke, and heart failure events, in those not having events, reclassification of participants to eGFR categories was superior using the CKD-EPI equation compared with the MDRD Study equation.

How to manage HIV-infected patients with chronic kidney disease in the HAART era

As human immunodeficiency virus (HIV)-infected patients now live longer while receiving highly active antiretroviral therapy (HAART), chronic kidney disease (CKD) has emerged as a significant cause of morbidity and mortality among urban HIV population. Risk factors associated with CKD in such HIV-infected population include aging, hypertension, diabetes mellitus, co-infection with hepatitis C virus, low CD4 cell count, and high HIV viral load. Clinical experience has shown that HIV-infected individuals often have one or more concurrent risk factors for CKD. The cumulative effect of multiple risk factors on the development of CKD should be noted in this population. Glomerular disease directly related to HIV infection, so-called HIV-associated nephropathy, remains an important cause of CKD among limited HIV population of African descent. The impact of exposure to nephrotoxic antiretroviral agents on the development of kidney disease is both an old and a new concern. In particular, the association of tenofovir with kidney disease has been an area of great interest. The findings regarding tenofovir's adverse effect on long-term kidney function vary among studies. Early identification and treatment of kidney disease is imperative for reducing the burden of patients requiring dialysis in HIV-infected populations. Periodic monitoring of urinary albumin excretion, tubular parameters such as low-molecular-weight proteinuria, and the estimated glomerular filtration rate may be useful for early diagnosis of patients at risk for incident CKD. This review focuses on recent developments in epidemiology, risk factors, identification, estimation, and management of CKD in HIV-infected population in the HAART era.

Demystifying ethnic/sex differences in kidney function: is the difference in (estimating) glomerular filtration rate or in serum creatinine concentration?

BACKGROUND

The recent evaluation of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation for estimating the glomerular filtration rate (GFR) in multiple ethnicities has raised the question on how well this equation performs for African-American and Asian subjects. There is no doubt that serum creatinine (Scr) concentration differs between ethnicities and sexes. We show that creatinine-based equations for white populations may be inaccurate for estimating GFR in other ethnic/gender groups, especially in populations from Asia.

METHODS

This study presents a mathematical analysis of the CKD-EPI-equation complemented with a literature review of median and reference values for IDMS-standardized Scr-concentrations for multiple ethnicities.

RESULTS

The study shows that at equal eGFR-CKD-EPI-values, the ratio of Scr between females and males equals 0.79 and between other ethnicities/sexes and white males is constant too. From this information, it is possible to calculate mean Scr-values that correspond very well with literature values directly obtained from Scr-distributions in healthy white males and females and in black males, but the discrepancy is larger for other populations.

CONCLUSIONS

Our results confirm the criticism that has been raised for using the CKD-EPI-equation for these ethnicities. An alternative eGFR-model is proposed based on a population-normalized Scr that needs further validation.

Hepatitis C virus viremia increases the incidence of chronic kidney disease in HIV-infected patients

BACKGROUND

Several studies have reported on an association between hepatitis C virus (HCV) antibody status and the development of chronic kidney disease (CKD), but the role of HCV viremia and genotype are not well defined.

METHODS

Patients with at least three serum creatinine measurements after 1 January 2004 and known HCV antibody status were included. Baseline was defined as the first eligible estimated glomerular filtration rate (eGFR) (Cockcroft-Gault equation), and CKD was either a confirmed (>3 months apart) eGFR of 60 ml/min per 1.73 m or less for patients with a baseline eGFR more than 60 ml/min per 1.73 m or a confirmed 25% decline in eGFR for patients with a baseline eGFR of 60 ml/min per 1.73 m or less. Incidence rates of CKD were compared between HCV groups (anti-HCV-negative, anti-HCV-positive with or without viremia) using Poisson regression.

RESULTS

Of 8235 patients with known anti-HCV status, 2052 (24.9%) were anti-HCV-positive of whom 983 (47.9%) were HCV-RNA-positive, 193 (9.4%) HCV-RNA-negative and 876 (42.7%) had unknown HCV-RNA. At baseline, the median eGFR was 97.6 (interquartile range 83.8-113.0) ml/min per 1.73 m. During 36123 person-years of follow-up (PYFU), 495 patients progressed to CKD (6.0%) with an incidence rate of 14.5 per 1000 PYFU (95% confidence interval 12.5-14.9). In a multivariate Poisson model, patients who were anti-HCV-positive with HCV viremia had a higher incidence rate of CKD, whereas patients with cleared HCV infection had a similar incidence rate of CKD compared with anti-HCV-negative patients. There was no association between CKD and HCV genotype.

CONCLUSION

Compared with HIV-monoinfected patients, HIV-positive patients with chronic rather than cleared HCV infection were at increased risk of developing CKD, suggesting a contribution from active HCV infection toward the pathogenesis of CKD.

Renal Resistive Index and Cardiovascular and Renal Outcomes in Essential Hypertension

Increased renal restive index (RI) measured using Doppler ultrasonography has been shown to correlate with the degree of renal impairment in hypertensive patients. We investigated the prognostic role of RI in cardiovascular and renal outcomes. A total of 426 essential hypertensive subjects (mean age, 63 years; 50% female) with no previous cardiovascular disease were included in this study. Renal segmental arterial RI was measured by duplex Doppler ultrasonography. During follow-up (mean, 3.1 years), 57 participants developed the primary composite end points including cardiovascular and renal outcomes. In multivariate Cox regression analysis, RI was an independent predictor of worse outcome in total subjects (hazard ratio, 1.71 for 1 SD increase), as well as in patients with estimated glomerular filtration rate (eGFR) <60 mL/min per 1.73 m 2 (hazard ratio, 2.11 for 1 SD increase; P <0.01, respectively). When divided into 4 groups based on the respective sex-specific median levels of RI in the eGFR ≥60 and eGFR <60 mL/min per 1.73 m 2 groups, the group with eGFR <60 and high RI (male ≥0.73, female ≥0.72) had a significantly poorer event-free survival rate (χ 2 =126.4; P <0.01), and the adjusted hazard ratio by multivariate Cox regression analysis was 9.58 (95% CI, 3.26–32.89; P <0.01). In conclusion, impairment of renal hemodynamics evaluated by increased RI is associated with an increased risk of primary composite end points, and the combination of high RI and low eGFR is a powerful predictor of these diseases in essential hypertension. In hypertensive patients with chronic kidney disease, RI evaluation may complement predictors of cardiovascular and renal outcomes.

GFR estimation using standardized serum cystatin C in Japan

BACKGROUND

Recently, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) developed glomerular filtration rate (GFR)-estimating equations based on standardized serum cystatin C (CKD-EPI(cys)) and standardized serum creatinine plus standardized serum cystatin C (CKD-EPI(cr-cys)). We developed new GFR-estimating equations based on standardized cystatin C for a Japanese population and compared their accuracy with the CKD-EPI equations.

STUDY DESIGN

Accuracy of diagnostic test study.

SETTING & PARTICIPANTS

413 (development data set) and 350 individuals (validation data set).

INDEX TEST

CKD-EPI(cys); CKD-EPI(cr-cys); modifications to CKD-EPI(cys) and CKD-EPI(cr-cys) using Japanese coefficients; and newly developed Japanese eGFR equations based on standardized serum cystatin C (Eq(cys)), cystatin C with a nonrenal factor reflecting hypothesized extrarenal elimination (Eq(cys+nonrenal)), and creatinine in combination with cystatin C (Eq(cr-cys)). Standardized cystatin C values were determined by a colloidal gold immunoassay traceable to the international certified reference material ERM-DA471/IFCC.

REFERENCE TEST

Measured GFR by inulin renal clearance.

RESULTS

In a development data set, we calculated Japanese coefficients for CKD-EPI(cys) and CKD-EPI(cr-cys) of 0.977 (95% CI, 0.853-1.002) and 0.908 (95% CI, 0.889-0.928), respectively. In a validation data set, we compared CKD-EPI(cys), Eq(cys), and Eq(cys+nonrenal) with each other. Bias and accuracy were not significantly different among the 3 equations. The precision of CKD-EPI(cys) was significantly better than for Eq(cys) (P = 0.007) and not significantly different from Eq(cys+nonrenal) (P = 0.6). We then compared 0.908 × CKD-EPI(cr-cys), Eq(cr-cys), and Eq(average) (the average value of Eq(cr) [previous Japanese equation based on standardized serum creatinine] and Eq(cys+nonrenal)) with each other in the validation data set. Bias and accuracy were not significantly different among the 3 equations. The precision of 0.908 × CKD-EPI(cr-cys) was significantly better than for Eq(cr-cys) (P = 0.004) and not significantly different from Eq(average) (P = 0.06).

LIMITATIONS

Limited number of participants with measured GFR >90 mL/min/1.73 m(2). Extrarenal elimination of cystatin C was not measured.

CONCLUSIONS

CKD-EPI(cys) performed well in Japanese individuals, suggesting that equations based on serum cystatin C could be used in patients with different races without modification. Accounting for extrarenal elimination of cystatin C may improve the performance of estimating equations.

Hepatitis B and C co-infection are independent predictors of progressive kidney disease in HIV-positive, antiretroviral-treated adults

Chronic kidney disease (CKD) is an important cause of morbidity and mortality in HIV-positive individuals. Hepatitis C (HCV) co-infection has been associated with increased risk of CKD, but prior studies lack information on potential mechanisms. We evaluated the association between HCV or hepatitis B (HBV) co-infection and progressive CKD among 3,441 antiretroviral-treated clinical trial participants. Progressive CKD was defined as the composite of end-stage renal disease, renal death, or significant glomerular filtration rate (eGFR) decline (25% decline to eGFR <60 mL/min/1.73 m(2) or 25% decline with a baseline <60). Generalized Estimating Equations were used to model the odds of progressive CKD. At baseline, 13.8% and 3.3% of participants were co-infected with HCV and HBV, respectively. Median eGFR was 111, and 3.7% developed progressive CKD. After adjustment, the odds of progressive CKD were increased in participants with HCV (OR 1.72, 95% CI 1.07-2.76) or HBV (OR 2.26, 95% CI 1.15-4.44). Participants with undetectable or low HCV-RNA had similar odds of progressive CKD as HCV seronegative participants, while participants with HCV-RNA >800,000 IU/ml had increased odds (OR 3.07; 95% CI 1.60-5.90). Interleukin-6, hyaluronic acid, and the FIB-4 hepatic fibrosis index were higher among participants who developed progressive CKD, but were no longer associated with progressive CKD after adjustment. Future studies should validate the relationship between HCV viremia and CKD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00027352; NCT00004978.

Meta-analysis identifies multiple loci associated with kidney function-related traits in east Asian populations

Chronic kidney disease (CKD), impairment of kidney function, is a serious public health problem, and the assessment of genetic factors influencing kidney function has substantial clinical relevance. Here, we report a meta-analysis of genome-wide association studies for kidney function-related traits, including 71,149 east Asian individuals from 18 studies in 11 population-, hospital- or family-based cohorts, conducted as part of the Asian Genetic Epidemiology Network (AGEN). Our meta-analysis identified 17 loci newly associated with kidney function-related traits, including the concentrations of blood urea nitrogen, uric acid and serum creatinine and estimated glomerular filtration rate based on serum creatinine levels (eGFRcrea) (P < 5.0 × 10(-8)). We further examined these loci with in silico replication in individuals of European ancestry from the KidneyGen, CKDGen and GUGC consortia, including a combined total of ∼110,347 individuals. We identify pleiotropic associations among these loci with kidney function-related traits and risk of CKD. These findings provide new insights into the genetics of kidney function.

Serum allograft inflammatory factor-1 is a novel marker for diabetic nephropathy

AIMS

Recent studies have identified macrophage-mediated injury as an important component in the development of diabetic nephropathy. The aim of this study was to investigate the correlations between serum allograft inflammatory factor-1 (AIF-1) concentration, which is a marker of activated macrophages, and diabetic nephropathy.

METHODS

Serum AIF-1 concentrations were measured in 284 patients with type 2 diabetes. We evaluated relationships of serum AIF-1 concentrations to degree of urinary albumin excretion (UAE) or estimated glomerular filtration rate (eGFR) in univariate and multivariate linear regression analyses.

RESULTS

Serum AIF-1 concentrations positively correlated with logarithm of UAE (r=0.260, P<0.0001), whereas serum AIF-1 concentrations inversely correlated with eGFR (r=-0.312, P<0.0001). Mean serum AIF-1 concentration was higher in patients with macroalbuminuria than that in patients with normoalbuminuria (P=0.0001) or that in patients with microalbuminuria (P=0.0093). In multivariate linear regression analyses, serum AIF-1 concentrations were independently correlated with logarithm of UAE (β=0.213, P=0.0120) and with eGFR (β=-0.286, P=0.0011).

CONCLUSIONS

Serum AIF-1 concentration correlated with albuminuria and eGFR in patients with type 2 diabetes and it could be a marker of diabetic nephropathy as well as activated macrophages.

Chronic kidney disease categories and renal-cardiovascular outcomes in type 2 diabetes without prevalent cardiovascular disease: a prospective cohort study (JDDM25)

AIMS/HYPOTHESIS

In type 2 diabetic patients at low risk for cardiovascular disease (CVD), the relationship between the clinical course of nephropathy by stage of chronic kidney disease (CKD) and onset of CVD remains unclear. Clarification of this relationship is important for clinical decision-making for both low- and high-risk diabetic patients.

METHODS

This 4 year prospective study enrolled 2,954 type 2 diabetic patients with no prevalent CVD, and serum creatinine <176.8 μmol/l. The risk for CVD onset (non-fatal and fatal CVD and stroke, and peripheral arterial disease) was assessed according to CKD stage categorised by urinary albumin-to-creatinine ratio (ACR; mg/mmol) and estimated GFR (eGFR; ml min(-1) 1.73 m(-2)). Association of progression from 'no CKD' stage (ACR <3.5 mg/mmol and eGFR ≥ 90 ml min(-1) 1.73 m(-2)) with risk for CVD onset was also evaluated.

RESULTS

During follow-up (median 3.8 years), 89 CVD events occurred. Compared with patients with 'no CKD' as reference, those with ACR ≥ 35.0 mg/mmol with co-existing eGFR 60-89 ml min(-1) 1.73 m(-2) or <60 ml min(-1) 1.73 m(-2) showed increased risk for CVD onset, whereas those with eGFR ≥ 90 ml min(-1) 1.73 m(-2) did not. Those with ACR <3.5 mg/mmol and eGFR <60 ml min(-1) 1.73 m(-2) did not show any increased risk. Among patients with 'no CKD' stage at baseline, those who progressed to ACR ≥ 3.5 mg/mmol during follow-up showed an increased risk compared with those who did not, whereas those who progressed to eGFR <90 ml min(-1) 1.73 m(-2) did not have increased risk.

CONCLUSIONS/INTERPRETATION

The risk for CVD was associated with progression of albuminuria stage rather than eGFR stage in type 2 diabetic patients at relatively low risk for CVD.

The impact of different GFR estimating equations on the prevalence of CKD and risk groups in a Southeast Asian cohort using the new KDIGO guidelines

Background

Recently, the Kidney Disease: Improving Global Outcomes (KDIGO) group recommended that patients with CKD should be assigned to stages and composite relative risk groups according to GFR (G) and proteinuria (A) criteria. Asians have among the highest rates of ESRD in the world, but establishing the prevalence and prognosis CKD is a problem for Asian populations since there is no consensus on the best GFR estimating (eGFR) equation. We studied the effects of the choice of new Asian and Caucasian eGFR equations on CKD prevalence, stage distribution, and risk categorization using the new KDIGO classification.

Methods

The prevalence of CKD and composite relative risk groups defined by eGFR from with Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI); standard (S) or Chinese(C) MDRD; Japanese CKD-EPI (J-EPI), Thai GFR (T-GFR) equations were compared in a Thai cohort (n = 5526)

Results

There was a 7 fold difference in CKD_3-5 prevalence between J-EPI and the other Asian eGFR formulae. CKD_3-5 prevalence with S-MDRD and CKD-EPI were 2 - 3 folds higher than T-GFR or C-MDRD. The concordance with CKD-EPI to diagnose CKD_3-5 was over 90% for T-GFR or C-MDRD, but they only assigned the same CKD stage in 50% of the time. The choice of equation also caused large variations in each composite risk groups especially those with mildly increased risks. Different equations can lead to a reversal of male: female ratios. The variability of different equations is most apparent in older subjects. Stage G3aA1 increased with age and accounted for a large proportion of the differences in CKD_3-5 between CKD-EPI, S-MDRD and C-MDRD.

Conclusions

CKD prevalence, sex ratios, and KDIGO composite risk groupings varied widely depending on the equation used. More studies are needed to define the best equation for Asian populations.

Effect of obesity on declining beta cell function after diagnosis of type 2 diabetes: a possible link suggested by cross-sectional analysis

It has been reported that beta cell function progressively declines in patients with type 2 diabetes. The objective of this study was to assess the effect of obesity on declining beta cell function after diagnosis of type 2 diabetes. We conducted a cross-sectional study of 689 consecutive subjects with type 2 diabetes who were admitted to our hospital from 2000 to 2007. Fasting and postprandial serum C-peptide immunoreactivity (CPR) and urinary CPR levels had been measured during admission. The subjects were stratified according to BMI and time since diagnosis. CPR index was calculated as CPR (ng/mL) / plasma glucose (mg/dL) x 100. All CPR measurements were significantly higher in the 263 obese (BMI ≥25) subjects compared to the 426 lean subjects (BMI <25). There was a significant negative correlation between CPR indices and duration of diabetes, suggesting a progressive decline in beta cell function after diagnosis of type 2 diabetes. However, this decline was more apparent in obese subjects (postprandial CPR index 0.059/year) compared to lean subjects (0.025/year). The significant difference in serum CPR indices between the lean and obese subjects was lost in subjects more than 10 years after diagnosis. In conclusion, our observations suggest that beta cell function shows a greater progressive decline in obese subjects than in lean subjects with type 2 diabetes. Treatment of obesity may be an important strategy to preserve beta cell function in patients with type 2 diabetes.

A Case for Early Screening for Diabetic Kidney Disease

Chronic kidney disease (CKD) is a public health dilemma contributing to increasing global morbidity and mortality. There is increasing recognition that early detection and management of CKD is critical in delaying disease progression as well as improving mortality rates. However, kidney disease is a silent process and usually goes undetected until more advanced stages, wherein the opportunity to intervene and improve kidney-related outcome is diminished, since awareness of CKD is low in earlier stages. Herein, we will review the screening and detection strategies for CKD as well as the importance of intervention in early stages to reduce progression and also the burden of CKD.

Estimating glomerular filtration rate: comparison of the CKD-EPI and MDRD equations in a large UK cohort with particular emphasis on the effect of age

BACKGROUND

The chronic kidney disease (CKD)-Epidemiology Collaboration (CKD-EPI) equation was developed to address the underestimation of measured glomerular filtration rate (GFR) by the Modification of Diet in Renal Disease (MDRD) equation at levels >60 mL/min/1.73 m(2).

AIM

To assess the impact of the CKD-EPI equation on the estimation of GFR in a large adult UK population (n = 561,400), particularly looking at the effect of age.

DESIGN

Serum creatinine results (ID-MS-aligned enzymatic assay) were extracted from the pathology database during 1 year on adult (≥ 18 years) patients from primary care.

METHODS

The first available creatinine result from 174,448 people was used to estimate GFR using both equations and agreement assessed.

RESULTS

Median CKD-EPI GFR was significantly higher than median MDRD GFR (82 vs. 76 mL/min/1.73 m(2), P < 0.0001). Overall mean bias between CKD-EPI and MDRD GFR was 5.0%, ranging from 13.0% in the 18-29 years age group down to -7.5% in those aged ≥ 90 years. Although statistically significant at all age groups the difference diminished with age and the agreement in GFR category assignment increased. Age-adjusted population prevalence of CKD Stages 3-5 was lower by CKD-EPI than by MDRD (4.4% vs. 4.9%).

CONCLUSION

CKD-EPI produces higher GFR and lower CKD estimates, particularly among 18-59 year age groups with MDRD estimated GFRs of 45-59 mL/min/1.73 m(2) (Stage 3A). However, at ages >70 years there is very little difference between the equations, and among the very elderly CKD-EPI may actually increase CKD prevalence estimates.

Tolvaptan in autosomal dominant polycystic kidney disease: three years' experience

BACKGROUND AND OBJECTIVES

Autosomal dominant polycystic kidney disease (ADPKD), a frequent cause of end-stage renal disease, has no cure. V2-specific vasopressin receptor antagonists delay disease progression in animal models.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

This is a prospectively designed analysis of annual total kidney volume (TKV) and thrice annual estimated GFR (eGFR) measurements, from two 3-year studies of tolvaptan in 63 ADPKD subjects randomly matched 1:2 to historical controls by gender, hypertension, age, and baseline TKV or eGFR. Prespecified end points were group differences in log-TKV (primary) and eGFR (secondary) slopes for month 36 completers, using linear mixed model (LMM) analysis. Sensitivity analyses of primary and secondary end points included LMM using all subject data and mixed model repeated measures (MMRM) of change from baseline at each year. Pearson correlation tested the association between log-TKV and eGFR changes.

RESULTS

Fifty-one subjects (81%) completed 3 years of tolvaptan therapy; all experienced adverse events (AEs), with AEs accounting for six of 12 withdrawals. Baseline TKV (controls 1422, tolvaptan 1635 ml) and eGFR (both 62 ml/min per 1.73 m(2)) were similar. Control TKV increased 5.8% versus 1.7%/yr for tolvaptan (P < 0.001, estimated ratio of geometric mean 0.96 [95% confidence interval 0.95 to 0.97]). Corresponding annualized eGFR declined: -2.1 versus -0.71 ml/min per 1.73 m(2)/yr (P = 0.01, LMM group difference 1.1 ml/min per 1.73 m(2)/yr [95% confidence interval 0.24 to 1.9]). Sensitivity analyses including withdrawn subjects were similar, whereas MMRM analyses were significant at each year for TKV and nonsignificant for eGFR. Increasing TKV correlated with decreasing eGFR (r = -0.21, P < 0.01).

CONCLUSION

ADPKD cyst growth progresses more slowly with tolvaptan than in historical controls, but AEs are common.

Performance of serum cystatin C versus serum creatinine as a marker of glomerular filtration rate as measured by inulin renal clearance

INTRODUCTION

Serum cystatin C was recently proposed as an alternative marker of glomerular filtration rate (GFR), with a suggested better performance than creatinine. However, detailed studies are limited. We evaluated the performance of cystatin C as a GFR marker.

METHODS

GFR was measured by inulin clearance in 763 Japanese subjects. Factors other than GFR influencing serum cystatin C or serum creatinine were analyzed by multivariate analyses.

RESULTS

After adjustment for GFR, the value of serum creatinine was 25.2% lower in females than males, and decreased by 5.2% for every 20 years of age. Serum cystatin C was 8.2% lower in females, and did not change significantly with aging. Creatinine but not cystatin C was significantly affected by body weight, height and body mass index after adjustment for GFR, gender and age. The correlation coefficient between GFR and 1/cystatin C was significantly higher than that of 1/creatinine in total subjects (0.866 and 0.810, respectively, p < 0.001). Unlike serum creatinine, serum cystatin C did not increase in association with the reduction of GFR in subjects with very low GFR. The regression line of 1/cystatin C against GFR showed a significantly negative intercept of about -8 ml/min/1.73 m(2).

CONCLUSION

The performance of serum cystatin C was not good in the subjects with very low GFR. Non-renal elimination of cystatin C may contribute to the result. The correlation between reciprocal cystatin C and GFR suggested its superiority in predicting GFR compared to creatinine in subjects with normal and mildly reduced GFR.

Implication of CKD-EPI equation to estimate glomerular filtration rate in Chinese patients with chronic kidney disease

OBJECTIVE

To evaluate the applicability of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation to estimate glomerular filtration rate (GFR) in Chinese patients of different stages of CKD.

METHODS

The CKD-EPI equation estimated GFR (eGFR) was compared with body surface area standardized GFR (sGFR), which was measured by diethylenetriaminepentaacetic acid renal dynamic imaging method in 142 CKD cases.

RESULTS

eGFR was positively correlated with sGFR (r = 0.838, p < 0.001). eGFR of 15%, 30%, and 50% accuracy were 31.0%, 57.7%, and 76.8%, respectively. Average deviation of eGFR from sGFR was -0.92 ± 16.36 mL/min/1.73 m2 (p = 0.506). There was no significant deviation in the CKD from stages 2 to 5. However, in CKD stage 1, the deviation was increased with the value of 13.36 ± 18.44 mL/min/1.73 m(2) (p = 0.023).

CONCLUSION

CKD-EPI equation might be widely used in evaluation of Chinese CKD patients of different stages, with a less deviation and higher accuracy. However, in CKD stage 1, eGFR was higher than sGFR on average. It was suggested that eGFR might be overcorrected or overestimated. These results demonstrated that careful modification of CKD-EPI equation would be necessary in Chinese populations with CKD.

Evaluation of the Chronic Kidney Disease Epidemiology Collaboration equation for estimating the glomerular filtration rate in multiple ethnicities

An equation from the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) provides more accurate estimates of the glomerular filtration rate (eGFR) than that from the modification of diet in renal disease (MDRD) Study, although both include a two-level variable for race (Black and White and other). Since creatinine generation differs among ethnic groups, it is possible that a multilevel ethnic variable would allow more accurate estimates across all groups. To evaluate this, we developed an equation to calculate eGFR that includes a four-level race variable (Black, Asian, Native American and Hispanic, and White and other) using a database of 8254 patients pooled from 10 studies. This equation was then validated in 4014 patients using 17 additional studies from the United States and Europe (validation database), and in 1022 patients from China (675), Japan (248), and South Africa (99). Coefficients for the Black, Asian, and Native American and Hispanic groups resulted in 15, 5, and 1% higher levels of eGFR, respectively, compared with the White and other group. In the validation database, the two-level race equation had minimal bias in Black, Native American and Hispanic, and White and other cohorts. The four-level ethnicity equation significantly improved bias in Asians of the validation data set and in Chinese. Both equations had a large bias in Japanese and South African patients. Thus, heterogeneity in performance among the ethnic and geographic groups precludes use of the four-level race equation. The CKD-EPI two-level race equation can be used in the United States and Europe across a wide range of ethnicity.

Postprandial serum C-peptide to plasma glucose ratio as a predictor of subsequent insulin treatment in patients with type 2 diabetes

Type 2 diabetes is a progressive disease and most patients with type 2 diabetes eventually need insulin therapy. The objective of this study was to clarify C-peptide immunoreactivity (CPR), a marker of beta cell function, as a predictor of requirement for insulin therapy. We conducted a retrospective study of 579 consecutive subjects with type 2 diabetes who were admitted to our hospital from 2000 to 2007 and were able to be followed up for at least 6 months after discharge. Fasting and postprandial serum CPR and urinary CPR levels had been measured during admission. Information about insulin therapy at the last visit was obtained from medical records. At the last visit, 364 subjects (62.9%) were treated with insulin. Mean interval between discharge and the last visit was 4.5 ± 2.3 years. Serum and urine CPR levels at baseline were significantly associated with insulin treatment at the last visit (P<0.001 for all). Among CPR values, postprandial serum CPR to plasma glucose ratio (CPR index) showed the greatest area under the receiver operating characteristic (ROC) curve for insulin therapy. Multivariate logistic regression analysis evaluating the effect of postprandial CPR index adjusted for other confounders showed consistent results with unadjusted results. In conclusion, beta cell dysfunction is significantly correlated with future insulin therapy in patients with type 2 diabetes. Our study indicates that among CPR measurements, postprandial CPR index is the best predictive marker for future insulin therapy.

Chronic kidney disease: a large-scale population-based study of the effects of introducing the CKD-EPI formula for eGFR reporting

Objective To evaluate the effects of introducing the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) formula for estimated glomerular filtration rate (eGFR) reporting in the adult population in routine clinical practice with clinician-directed testing. Design Retrospective study of all creatinine measurements and calculation of eGFRs using Modification of Diet in Renal Disease (MDRD) and CKD-EPI formulae. Setting General population, Oxfordshire, UK. Participants An unselected population of around 660 000. Interventions Reporting of eGFRs using MDRD or CKD-EPI formulae. Primary and secondary outcome measures Evaluation of the effects of the CKD-EPI formula on the prevalence of different stages of chronic kidney disease (CKD). Results The CKD-EPI formula reduced the prevalence of CKD (stages 2-5) by 16.4% in patients tested in primary care. At the important stage 2-stage 3 cut-off, there was a relative reduction of 7.5% in the prevalence of CKD stages 3-5 from 15.7% to 14.5%. The CKD-EPI formula reduced the prevalence of CKD stages 3-5 in those aged <70 but increased it at ages >70. Above 70 years, the prevalence of stages 3-5 was similar with both equations for women (around 41.2%) but rose in men from 33.3% to 35.5%. CKD stages 4-5 rose by 15% due exclusively to increases in the over 70s, which could increase specialist referral rates. The CKD classification of 18.3% of all individuals who had a creatinine measurement was altered by a change from the MDRD to the CKD-EPI formula. In the UK population, the classification of up to 3 million patients could be altered, the prevalence of CKD could be reduced by up to 1.9 million and the prevalence of CKD stages 3-5 could fall by around 200 000. Conclusions Introduction of the CKD-EPI formula for eGFR reporting will reduce the prevalence of CKD in a primary care setting with current testing practice but will raise the prevalence in the over 70s age group. This has implications for clinical practice, healthcare policy and current prevalence-based funding arrangements.