Do healthy potential kidney donors in india have an average glomerular filtration rate of 81.4 ml/min?

Has the time come for age-adapted glomerular filtration rate criteria to define chronic kidney disease: how soon is now?

PURPOSE OF REVIEW

The conventional definition of chronic kidney disease (CKD) primarily relies on the identification of albuminuria or a decline in estimated glomerular filtration rate (eGFR). For many years, a straightforward eGFR threshold of <60 ml/min/1.73 m 2 has been widely adopted as the standard for defining CKD. Nonetheless, this criterion fails to consider the natural aging process of the kidney, and this oversight may affect the accurate diagnosis of kidney disease particularly at the extremes of age.

RECENT FINDINGS

The fixed eGFR threshold of <60 ml/min/1.73 m 2 for defining CKD misses crucial opportunities for risk prevention. Studies have revealed that the eGFR threshold at which the risks for adverse long-term health outcomes such as mortality, cardiovascular events, and kidney failure begin to rise varies substantially by age. Specifically, this threshold is lower for the elderly and higher for young adults. Consequently, this results in the over-diagnosis of kidney disease in the elderly and the under-diagnosis of kidney disease in young adults.

SUMMARY

To address these limitations of the current CKD definition, we discuss a number of proposed age-adapted eGFR criteria and weigh their pros and cons against the current, simple, and universally accepted approach.

Whole and cortical kidney volume predict 5-year post-nephrectomy eGFR in Indian living kidney donors

AIM

To study the additional utility of pre-nephrectomy whole and cortical kidney volumes (WKV, CKV) in predicting long-term post-nephrectomy kidney function in Indian living kidney donors (LKDs).

METHODS

This retrospective cohort study included all LKDs who underwent nephrectomy between 1 January 2006 and 31 December 2015 at our centre, had pre-nephrectomy height, weight and computed tomography (CT) angiography with arterial and nephrographic phase documented, and 5-year post-nephrectomy creatinine values measured. Correlation between body surface area (BSA) adjusted pre-nephrectomy total CKV, WKV and pre-nephrectomy CKD EPI eGFR; BSA-adjusted remnant pre-nephrectomy CKV (rCKV), WKV (rWKV) and 5-year post-nephrectomy CKD EPI creatinine eGFR (5yeGFRCr ); predictors of 5yeGFRCr  < 70% of pre-nephrectomy CKD EPI creatinine eGFR (pre-eGFRCr ), and an equation to predict 5yeGFRCr from pre-nephrectomy variables were calculated.

RESULTS

A total of 196 LKDs (74% female, mean age 41.7 ± 11.0 years) were included in the study. Total WKV showed higher correlation with pre-nephrectomy eGFR than CKV, the highest with CKD EPI cystatin eGFR. Remnant WKV showed higher correlation than rCKV with post-nephrectomy eGFRCr and this increased over time. Older age, lower rWKV or rCKV, higher BSA, and higher pre-eGFRCr identified LKDs with 5yeGFRCr  < 70% of pre-eGFRCr , with rCKV identifying a higher proportion (4.5%) of such LKDs. A model including rWKV or rCKV predicted 5yeGFRCr better than one including age, gender, BSA and pre-eGFRCr alone.

CONCLUSION

Inclusion of pre-nephrectomy remnant CKV and WKV into models for 5yeGFRCr and sub-optimal post-nephrectomy adaptation in Indian LKDs improves their accuracy. CKD EPI cystatin eGFR correlates better with functional renal mass.

Age-adapted percentiles of measured glomerular filtration in healthy individuals: extrapolation to living kidney donors over 65 years

OBJECTIVES

Most data on glomerular filtration rate (GFR) originate from subjects <65 years old, complicating decision-making in elderly living kidney donors. In this retrospective multi-center study, we calculated percentiles of measured GFR (mGFR) in donors <65 years old and extrapolated these to donors ≥65 years old.

METHODS

mGFR percentiles were calculated from a development cohort of French/Belgian living kidney donors <65 years (n=1,983), using quantiles modeled as cubic splines (two linear parts joining at 40 years). Percentiles were extrapolated and validated in an internal cohort of donors ≥65 years (n=147, France) and external cohort of donors and healthy subjects ≥65 years (n=329, Germany, Sweden, Norway, France, The Netherlands) by calculating percentages within the extrapolated 5th-95th percentile (P5-P95).

RESULTS

Individuals in the development cohort had a higher mGFR (99.9 ± 16.4 vs. 86.4 ± 14 and 82.7 ± 15.5 mL/min/1.73 m²) compared to the individuals in the validation cohorts. In the internal validation cohort, none (0%) had mGFR below the extrapolated P5, 12 (8.2%) above P95 and 135 (91.8%) between P5-P95. In the external validation cohort, five subjects had mGFR below the extrapolated P5 (1.5%), 25 above P95 (7.6%) and 299 (90.9%) between P5-P95.

CONCLUSIONS

We demonstrate that extrapolation of mGFR from younger donors is possible and might aid with decision-making in elderly donors.

Reference values of glomerular filtration rate for healthy adults in southern China: a cross-sectional survey

Background:

Currently the global data on the glomerular filtration rate of healthy adults are insufficient, with relatively little data for other races and countries. Especially in China, there are no such figures.

Methods:

In this cross-sectional study, we included healthy Han adults in southern China. Participants completed a lifestyle and medical history questionnaire and had their blood pressure measured, and blood and urine samples collected. Serum creatinine was measured and used to estimated glomerular filtration rate (eGFR) by the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formulae. The normal range of eGFR is described, and the influence of gender and age on eGFR is analyzed by the statistical method.

Results:

We provided the largest sample size of eGFR research in China at present. The mean age of the 20,930 healthy individuals was 40.9 ± 12.3 years, 58.8% were women. The eGFR_MDRD for women and men were 111.3 ± 17.4 mL/min per 1.73 m² and 103.3 ± 15.9 mL/min per 1.73 m², respectively. The eGFR_CKD-EPI for women and men were 110.3 ± 12.1 mL/min per 1.73 m² and 103.8 ± 13.3 mL/min per 1.73 m², respectively. The eGFR_MDRD of women and men in all age groups decreased continuously by 7.3 ml/min/1.73 m²/decade and 4.4 ml/min/1.73 m²/decade, respectively. The eGFR_CKD-EPI of women and men in all age groups decreased continuously by 8.4 ml/min/1.73 m²/decade and 6.9 ml/min/1.73 m²/decade.

Conclusions:

The eGFR of women is higher than men and with the increasing age, the eGFR of women declines faster than men.

CKD: A Call for an Age-Adapted Definition

Current criteria for the diagnosis of CKD in adults include persistent signs of kidney damage, such as increased urine albumin-to-creatinine ratio or a GFR below the threshold of 60 ml/min per 1.73 m2 This threshold has important caveats because it does not separate kidney disease from kidney aging, and therefore does not hold for all ages. In an extensive review of the literature, we found that GFR declines with healthy aging without any overt signs of compensation (such as elevated single-nephron GFR) or kidney damage. Older living kidney donors, who are carefully selected based on good health, have a lower predonation GFR compared with younger donors. Furthermore, the results from the large meta-analyses conducted by the CKD Prognosis Consortium and from numerous other studies indicate that the GFR threshold above which the risk of mortality is increased is not consistent across all ages. Among younger persons, mortality is increased at GFR <75 ml/min per 1.73 m2, whereas in elderly people it is increased at levels <45 ml/min per 1.73 m2 Therefore, we suggest that amending the CKD definition to include age-specific thresholds for GFR. The implications of an updated definition are far reaching. Having fewer healthy elderly individuals diagnosed with CKD could help reduce inappropriate care and its associated adverse effects. Global prevalence estimates for CKD would be substantially reduced. Also, using an age-specific threshold for younger persons might lead to earlier identification of CKD onset for such individuals, at a point when progressive kidney damage may still be preventable.

Measured (and estimated) glomerular filtration rate: reference values in West Africa

Background

Establishment of normal reference values for glomerular filtration rate (GFR) is mandatory in nephrology. However, no data are available for measured GFR (mGFR) in Africa.

Methods

GFR was measured in 237 healthy adult subjects (103 women and 134 men, mean age 34 ± 10 years) by iohexol plasma clearance.

Results

The mean mGFR was 103 ± 17 mL/min/1.73 m2 and the median value was 103 mL/min/1.73 m2 (2.5th and 97.5th percentiles are 76 and 137 mL/min/1.73 m2, respectively). No significant difference in mGFR results was observed in patients < 40 years of age, whereas a significant decline in mGFR was observed after 40 years of age. There was no significant difference between mGFR in men and women.

Conclusions

Normal GFR values and descriptions of percentiles are now available for West Africa. As in Caucasians, no significant difference was observed between men and women. Moreover, the same age-associated decline in mGFR is also observed after 40 years of age, as in Caucasians.

Prevalence of and risk factors for chronic kidney disease of unknown aetiology in India: secondary data analysis of three population-based cross-sectional studies

OBJECTIVES

To assess whether chronic kidney disease of unknown aetiology (CKDu) is present in India and to identify risk factors for it using population-based data and standardised methods.

DESIGN

Secondary data analysis of three population-based cross-sectional studies conducted between 2010 and 2014.

SETTING

Urban and rural areas of Northern India (states of Delhi and Haryana) and Southern India (states of Tamil Nadu and Andhra Pradesh).

PARTICIPANTS

12 500 individuals without diabetes, hypertension or heavy proteinuria.

OUTCOME MEASURES

Mean estimated glomerular filtration rate (eGFR) and prevalence of eGFR below 60 mL/min per 1.73 m2 (eGFR <60) in individuals without diabetes, hypertension or heavy proteinuria (proxy definition of CKDu).

RESULTS

The mean eGFR was 105.0±17.8 mL/min per 1.73 m2. The prevalence of eGFR <60 was 1.6% (95% CI=1.4 to 1.7), but this figure varied markedly between areas, being highest in rural areas of Southern Indian (4.8% (3.8 to 5.8)). In Northern India, older age was the only risk factor associated with lower mean eGFR and eGFR <60 (regression coefficient (95% CI)=-0.94 (0.97 to 0.91); OR (95% CI)=1.10 (1.08 to 1.11)). In Southern India, risk factors for lower mean eGFR and eGFR <60, respectively, were residence in a rural area (-7.78 (-8.69 to -6.86); 4.95 (2.61 to 9.39)), older age (-0.90 (-0.93 to -0.86); 1.06 (1.04 to 1.08)) and less education (-0.94 (-1.32 to -0.56); 0.67 (0.50 to 0.90) for each 5 years at school).

CONCLUSIONS

CKDu is present in India and is not confined to Central America and Sri Lanka. Identified risk factors are consistent with risk factors previously reported for CKDu in Central America and Sri Lanka.

Short-Term Outcomes in Newly Diagnosed Atrial Fibrillation and Chronic Kidney Disease: How Important Is Ethnicity?

See Article by Goto et al.

Renal Dysfunction in Patients With Nonalcoholic Fatty Liver Disease is Related to the Presence of Diabetes Mellitus and Severity of Liver Disease

BACKGROUND AND AIMS

There is sparse data on the prevalence of renal dysfunction in patients with nonalcoholic fatty liver disease (NAFLD). The aim of the present study was to evaluate the presence of renal dysfunction in patients with NAFLD and correlate it with the severity of liver disease.

METHODS

One hundred nonalcoholic patients with ultrasound showing hepatic steatosis were enrolled into the study after exclusion of other causes. Presence of renal dysfunction was estimated by glomerular filtration rate and by evaluating 24 h urinary protein and microalbumin. Various risk factors including components of metabolic syndrome, severity of hepatic steatosis (as assessed on ultrasound), hepatic necro-inflammation (as assessed by hepatic transaminases) and hepatic fibrosis (as assessed by transient elastography) were correlated with the presence of renal dysfunction.

RESULTS

Twenty eight (28%) patients with NAFLD had evidence of impaired renal function with 5 (5%) having abnormal glomerular filtration rate, 18 (18%) having significant proteinuria and 5 (5%) having both. Presence of type 2 diabetes mellitus, raised hepatic transaminases and advanced fibrosis on transient elastography were found as independent predictors of impaired renal function with raised hepatic transaminases having the best sensitivity (89%) and presence of advanced fibrosis the best specificity (90%). A model comprising of these three parameters had good accuracy (AUROC = 0.763) in predicting impaired renal function in patients with NAFLD.

CONCLUSIONS

Around one-third of patients with NAFLD have impaired renal functions. Prevalence of impaired renal function in patients with NAFLD is dependent on the severity of liver disease and presence of diabetes mellitus.

Glomerular filtration rate: new age- and gender- specific reference ranges and thresholds for living kidney donation

BACKGROUND

There is a need for a large, contemporary, multi-centre series of measured glomerular filtration rates (mGFR) from healthy individuals to determine age- and gender-specific reference ranges for GFR. We aimed to address this and to use the ranges to provide age- and gender-specific advisory GFR thresholds considered acceptable for living kidney donation.

METHODS

Individual-level data including pre-donation mGFR from 2974 prospective living kidney donors from 18 UK renal centres performed between 2003 and 2015 were amalgamated. Age- and gender-specific GFR reference ranges were determined by segmented multiple linear regression and presented as means ± two standard deviations.

RESULTS

Males had a higher GFR than females (92.0 vs 88.1 mL/min/1.73m2, P < 0.0001). Mean mGFR was 100 mL/min/1.73m2 until 35 years of age, following which there was a linear decline that was faster in females compared to males (7.7 vs 6.6 mL/min/1.73m2/decade, P = 0.013); 10.5% of individuals aged > 60 years had a GFR < 60 mL/min/1.73m2. The GFR ranges were used along with other published evidence to provide advisory age- and gender-specific GFR thresholds for living kidney donation.

CONCLUSIONS

These data suggest that GFR declines after 35 years of age, and the decline is faster in females. A significant proportion of the healthy population over 60 years of age have a GFR < 60 mL/min/1.73m2 which may have implications for the definition of chronic kidney disease. Age and gender differences in normal GFR can be used to determine advisory GFR thresholds for living kidney donation.

Relationship of Creatinine and Cystatin C-based Estimated Glomerular Filtration rates with Measured Glomerular Filtration Rate in Healthy Kidney Donors from South Asia

Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation is currently recommended for the estimation of glomerular filtration rate (GFR). This retrospective study aimed to evaluate the correlation between creatinine and cysC-based estimated GFRs and measured GFR in healthy adults. Consecutive healthy adults who were accepted as voluntary kidney donors at our center between January 2008 and December 2012 were included in the study. The 336 individuals who comprised the study population had a mean age of 41.6 ± 11.8 years, male:female ratio 1:1.7, mean creatinine 0.9 ± 0.1 mg/dl, and mean cysC 0.8 ± 0.1 mg/dl. Mean measured GFR by Tc-99m diethylenetriaminepentaacetic acid using Gates method was 98.4 ± 21.2 ml/min/1.73 m². The mean ± standard deviation of eGFRs by various formulae were as follows: Cockcroft–Gault (CG) = 88.1 ± 15.9 ml/min/1.73 m², Modification of Diet in Renal Disease (MDRD) = 78 ± 14.7 ml/min/1.73 m², CKD-EPI creatinine = 88.1 ± 15.5 ml/min/1.73 m², CKD-EPI cysC = 97 ± 19.9 ml/min/1.73 m², CKD-EPI creatinine-cysC (CKD-EPI cr-cysC) = 92.5 ± 14.1 ml/min/1.73 m². The CKD-EPI cr-cysC equation had the highest accuracy, with 43% and 72% of values lying within ±10% and ±20% of the measured GFR, respectively. Bland–Altman analyses for levels of agreement showed least bias with CKD-EPI cysC overall and among females, while among males, CKD-EPI creatinine equation had the least bias. The CKD-EPI equation showed a higher performance than the MDRD and CG equation in GFR estimation of a healthy population. Among CKD-EPI equations, CKD-EPI cr-cysC had the highest accuracy and CKD-EPI cysC the least bias.

Cisplatin Induced Renal Insufficiency Measured by Glomerular Filtration Rate with 99mTc-DTPA and by using Serum Creatinine based Formulae: A Prospective Study

INTRODUCTION

Cisplatin also known as Cis-Diammine-Dichloroplatinum (CDDP) is a chemotherapeutic alkylating nephrotoxic agent. Thus, it is necessary to know if renal function is normal before starting chemotherapy. Glomerular Filtration Rate (GFR) can be assessed directly by using a radiopharmaceutical (dGFR). Estimated GFR (eGFR) method use, Serum Creatinine (SCR) levels in mathematical formulae such as Cockroft-Gault (CG) and abbreviated. Modified Diet in Renal Disease (aMDRD). The serum creatinine level is a function of GFR but is relatively insensitive for detecting early renal insufficiency.

AIM

We aimed to correlate the incidence of Renal Insufficiency (RI) before and one month after completion of chemotherapy treatment by various methods.

MATERIALS AND METHODS

In this prospective study, we examined 64 patients with locally advanced head neck and uterine cervix cancers, before and one month after chemotherapy treatment with CDDP. Single agent CDDP was used with dose range between 35mg/m² as concurrent weekly chemotherapy.

RESULTS

Baseline RI was seen in 9.3% of patients by SCR levels, in 21.8% by the dGFR method, in 43.75% by the GFR-CG method and in 25% by the GFR-aMDRD formula. We considered GFR of <60 ml/min and SCR >1.5mg% as RI. After completion of treatment, the median RI was seen in 12.5% by SCR levels, 34.38% by dGFR method, 53.13% by GFR-CG method and 40.63% by GFR-aMDRD formula. None of the methods of GFR estimation showed statistically significant increase in RI one month after CDDP infusion. Only a weak correlation was seen between dGFR and eGFR based on SCR value (p=0.006).

CONCLUSION

Baseline RI was detected in 12% more cases when measured by dGFR as compared with SCR level. However, mathematical formulae overestimated baseline RI as compared to dGFR. One month after completion of treatment with CDDP chemotherapy, RI increased in 10%-15% cases as detected by all the four evaluated methods. There is weak correlation between SCR and dGFR thus implicating the importance of dGFR in assessing RI. Thus, despite normal SCR levels, GFR by radioisotope method should also be done as pre-treatment workup for cisplatin based chemotherapy.

The Role of Gender in Chronic Kidney Disease

Chronic kidney disease (CKD) is a common disease worldwide and is associated with high rates of morbidity and mortality. This review discusses several aspects of the relationship between gender and CKD. While the prevalence of CKD tends to be higher in women, the disease is more severe in men, who also have a higher prevalence of end-stage renal disease. Most of the evidence in the current literature suggests a higher progression rate and mortality risk of CKD in men compared with women, except in post-menopausal women and diabetic patients. However, the decrease in glomerular filtration rate and the increase in the level of albuminuria are more prominent mortality risk factors among women. Sex hormones are thought to play a major role in the biological mechanisms associated with variability in CKD prevalence and characteristics between men and women. Animal studies have demonstrated the harmful influence of testosterone and protective influence of oestrogen on several biological processes that are involved in kidney injury. However, the role of sex hormones in explaining gender-related differences in CKD in humans has not yet been established. In summary, gender has an important influence on several aspects of CKD. Further research is needed to find additional gender-related characteristics in CKD and to identify the mechanisms of sexual dimorphism in CKD.

Glomerular filtration rates in healthy Asians without kidney disease

AIM

The Chronic Kidney Disease Collaboration - Epidemiology (CKD-EPI) glomerular filtration rates (GFR) estimation equation is believed to estimate GFR more accurately in healthy people but this has not been validated in Asians. We studied the distribution of GFR in a multi-ethnic Asian population without CKD, and compared the performance of measures of GFR estimation, including the CKD-EPI equation, Cockroft-Gault equation, and 24-hour urine creatinine clearances.

MATERIALS AND METHODS

A total of 103 healthy volunteers without a history of kidney disease, hypertension, or diabetes underwent GFR measurement using 3-sample plasma clearance of (99m) Tc-DTPA. Cockroft-Gault estimated GFR and 24-hour urine creatinine clearances were normalized to body surface area.

RESULTS

The mean measured GFR was 101 ± 15.8 mL/min per 1.73 m(2) and was lowest in Indians (93 ± 12.3 mL/min per 1.73 m(2); P < 0.001). The CKD-EPI equation appears to be more accurate for healthy participants. Estimated GFR correlated with measured GFR (r = 0.57, P < 0.001), and the mean difference is 3.72 ± 14.43 mL/min per 1.73 m(2) (P < 0.001). However, estimating GFR using self-directed 24-hour urine creatinine clearances is poorer than using the CKD-EPI equation.

CONCLUSIONS

GFR estimation using self-directed 24-hour urine collection for creatinine clearance is less accurate than using the CKD-EPI equation. A larger study is required to clarify GFR in healthy Asians, and the association of health outcomes of Asian kidney donors with lower GFR thresholds.

Comparison of glomerular filtration rate measured by plasma sample technique, Cockroft Gault method and Gates' method in voluntary kidney donors and renal transplant recipients

Background:

There are numerous methods for calculation of glomerular filtration rate (GFR), which is a crucial measurement to identify patients with renal disease.

Aims:

The aim of this study is to compare four different methods of GFR calculation.

Settings and Design:

Clinical setup, prospective study.

Materials and Methods:

Data was collected from routine renal scans done for voluntary kidney donors (VKD) or renal transplant recipients 6 months after transplantation. Following technetium-99m diethylene triamine penta acetic acid injection, venous blood samples were collected from contralateral arm at 120, 180, and 240 min through an indwelling venous cannula and direct collection by syringe. A total volume of 1 ml of plasma from each sample and standards were counted in an automatic gamma counter for 1 min. Blood samples taken at 120 min and 240 min were used for double plasma sample method (DPSM) and a sample taken at 180 min for single plasma sample method (SPSM). Russell's formulae for SPSM and DPSM were used for GFR estimation. Gates’ method GFR was calculated by vendor provided software. Correlation analysis was performed using Pearson's correlation test.

Results:

SPSM correlated well with DPSM. GFR value in healthy potential kidney donors has a significant role in the selection of donors. The mean GFR ± (standard deviation) in VKD using SPSM, DPSM, camera depth method and Cockroft Gault method was 134.6 (25.9), 137.5 (42.4), 98.6 (15.9), 83.5 (21.1) respectively. Gates’ GFR calculation did not correlate well with plasma sampling method.

Conclusions:

Calculation of GFR plays a vital role in the management of renal patients, hence it was noted that Gates GFR may not be a reliable method of calculation. SPSM was more reliable. DPSM is reliable but cumbersome. It is difficult to accurately calculate GFR without a gold standard.

Reference values for glomerular filtration rate in healthy Brazilian adults

BACKGROUND

Glomerular filtration rate (GFR) is the best index of renal function, but age, gender and ethnicity can putatively affect its values. The aim of this study was to establish reference values for GFR in healthy Brazilian subjects while taking these factors into account.

METHODS

In this cross-sectional study, GFR was measured by the 51Cr-EDTA single-injection method. GFR reference values were developed according to CLSI Guidelines for Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory (CLSI C28 protocol).

RESULTS

The age range of the 285 healthy individuals was 19 to 70  years, 57% were females, and GFR was 106 ± 18 mL/min/1.73 m(2). There was no difference between male and female GFRs (108 ± 18 vs. 104 ± 18 mL/min/1.73 m(2) respectively, P = 0.134), and reference values were therefore developed from the pooled sample. GFR values were lower in subjects aged ≥45 years as compared with those younger than 45 years (98 ± 15 vs.112 ± 18 mL/min/1.73 m(2), P < 0.001). Based on mean ± 2 SD, GFR reference values were 76 to 148 mL/min/1.73 m(2) for subjects younger than 45 years and 68 to 128 mL/min/1.73 m(2) for individuals older than 45 years, irrespective of gender.

CONCLUSION

The age-adjusted reference intervals reported may be reliably adopted to evaluate kidney function, since they are based on recommended standards.

Do living kidney donors have CKD?

Living kidney donor transplantation is an increasingly used treatment for end-stage renal disease because it both confers excellent outcomes to transplant recipients, and is considered a safe procedure for prospective donors. The short- and long-term safety of prospective donors is paramount to the continued success of living donation. Although the initial experience with living kidney donors mostly included the healthiest donors, increasing need for organs and secular trends in the general population have subtly reshaped prevailing suitability criteria for donation. As the practice of living donation evolved over time, our understanding of kidney disease has also changed as we embraced the framework of the K-DOQI guidelines. It is not uncommon for donors to fit into some of the K-DOQI guidelines paradigms of risk and disease; however, whether there is a true biological consequence or whether it is a merely semantic conundrum remains unclear. Regardless, this is an important issue, and therefore future efforts should aim at addressing this matter.

Cystatin C as a marker of glomerular filtration rate in voluntary kidney donors

OBJECTIVES

Cystatin C is emerging as an endogenous marker of glomerular filtration rate. This study sought to assess the usefulness of serum cystatin C as a marker of glomerular filtration rate in comparison with serum creatinine and serum creatinine-based glomerular filtration rate estimations in voluntary kidney donors.

MATERIALS AND METHODS

Serum cystatin C and serum creatinine were estimated in 35 voluntary kidney donors. Glomerular filtration rate was estimated using: (1) Cockcroft-Gault method normalized to 1.73 m(2) of body surface area, (2) 4-variable Modification of Diet in Renal Diseases formula, and (3) (99m)Tc-DTPA double plasma sampling method. Glomerular filtration rate-double plasma sampling method was used as a reference value. Results were expressed as means ± SD.

RESULTS

The mean age of the participants was 44.23 ± 8.61 years old (19 women, 16 men). The mean serum creatinine was 0.83 ± 0.14 mg/dL, and the mean serum cystatin C was 0.71 ± 0.12 mg/L. Serum cystatin C showed significant correlation with serum creatinine (r = 0.864; P < .001). Glomerular filtration rate-MDRD showed the strongest correlation with glomerular filtration rate double plasma sampling method (r = 0.93; P < .001), followed by glomerular filtration rate-Cockcroft-Gault (r = 0.76; P < .001 ), serum creatinine (r = - 0.68; P < .001), and serum cystatin C (r = - 0.59; P < .001). The mean serum cystatin C values were 22.6% higher in men than in women. There was a significant correlation of serum cystatin C with glomerular filtration rate-Cockcroft-Gault (r = - 0.50; P = .002 ), glomerular filtration rate-MDRD (r = - 0.59; P < .001 ), and glomerular filtration rate-double plasma sampling method (r = - 0.59; P < .001 ).

CONCLUSIONS

Serum cystatin C is an optimal marker of glomerular filtration rate in voluntary kidney donors.

Level and determinants of kidney function in a South Asian population in Pakistan

BACKGROUND

People of South Asian origin are at high risk of chronic kidney disease. Some have suggested that the usual level of glomerular filtration rate (GFR) in South Asians may be lower than in populations of European origin. However, measured GFR in a general adult population of South Asian origin has not been studied.

DESIGN

Cross-sectional observational study.

SETTING & PARTICIPANTS

530 patients 40 years or older randomly selected from communities in Karachi, Pakistan, using multistage cluster sampling. Patients with both diabetes and hypertension were excluded.

PREDICTOR

Age, sex, diabetes, and hypertension.

OUTCOME

Measured GFR using urinary clearance of inulin.

RESULTS

Mean age of participants was 49.7 ± 9.5 (standard deviation [SD]) years, 51% were men, 34.9% had hypertension, and 30.5% had diabetes. Mean measured GFR was 94.1 ± 28.6 mL/min/1.73 m(2). GFR was lower by 0.79 ± 0.11 mL/min/1.73 m(2) for each 1-year older age. The 5-year age- and sex-specific mean GFR of the study population generally was within 1 SD of the mean of previously reported values for US adults. Factors independently associated with GFR were younger age (β coefficient, -3.84 [95% CI, -5.46 to -2.21] mL/min/1.73 m(2) per 5 years older), higher serum albumin level (4.58 [95% CI, 0.74-8.42] mL/min/1.73 m(2) per 0.5-g/dL increase), higher fasting plasma glucose level (0.81 [95% CI, 0.44-1.18] mL/min/1.73 m(2) per 10-mg/dL increase), high versus low meat intake (7.81 [95% CI, 1.14-14.48] mL/min/1.73 m(2) for ≥11 vs ≤5 servings/wk), and higher estimated protein intake (1.46 [95% CI, 0.41-2.51] mL/min/1.73 m(2) per 1.0-g/d increase) from urine urea nitrogen.

LIMITATIONS

Moderate sample size, lack of validation of some items in the dietary assessment for this study population.

CONCLUSIONS

Mean measured GFR in South Asian adults from the general population in Karachi, Pakistan, is only modestly lower than in European-origin counterparts, with similar age association. This may reflect lower dietary protein intake in South Asians.

Functional renal reserve capacity in different stages of chronic kidney disease

AIM

There is conflict in published reports on the extent of availability of the functional renal reserve (RR) in healthy adults and in various stages of chronic kidney disease (CKD). The aim of the present study was to determine the RR in various stages of CKD.

METHODS

Baseline glomerular filtration rate (GFR) and 'stimulated GFR' following amino acid infusion were measured in 25 volunteers and 100 patients at various stages of CKD by measuring plasma clearance of Tc99m diethyl triamine pentaacetic acid. Any obtained difference between stimulated and basal GFR was considered as RR and expressed as percentage.

RESULTS

The mean renal reserve was 23.4% in the healthy control group, 19.08% in CKD stage 1, 15.4% in CKD stage 2, 8.9% in CKD stage 3 and 6.7% in CKD stage 4, respectively.

CONCLUSION

Renal reserve falls relentlessly with progression of CKD from 23.4% in normal to 6.7% in stage 4 CKD. However, RR may also get completely exhausted even with a normal or with a minimal decline basal GFR. Kidneys may retain some RR even up to the GFR level of 15 mL/min.

Gender differences in age-related decline in glomerular filtration rates in healthy people and chronic kidney disease patients

Background

Since men with chronic kidney disease (CKD) progress faster than women, an accurate assessment of CKD progression rates should be based on gender differences in age-related decline of glomerular filtration rate (GFR) in healthy individuals.

Methods

A Chinese sample population from a stratified, multistage, and clustered CKD screening study was classified into healthy, at-risk, and CKD groups. The gender differences in estimated GFR (eGFR) and age-related eGFR decline were calculated for each group after controlling for blood pressure, fasting glucose levels, serum lipids levels, education level, and smoking status. After referencing to the healthy group, gender-specific multivariate-adjusted rates of decline in eGFR and differences in the rates of decline were calculated for both CKD and at-risk groups.

Results

The healthy, at-risk, and CKD groups consisted of 4569, 7434, and 1573 people, respectively. In all the 3 groups, the multivariate-adjusted eGFRs in men were lower than the corresponding eGFRs in women. In addition, in the healthy and at-risk groups, the rates of decline in eGFR in men were lower than the corresponding rates of decline in women (healthy group: 0.51 mL·min^-1·1.73 m^-2·yr^-1 vs. 0.74 mL·min^-1·1.73 m^-2·yr^-1 and at-risk group: 0.60 mL·min^-1·1.73 m^-2·yr^-1 vs. 0.73 mL·min^-1·1.73 m^-2·yr^-1). However, in the CKD group, the rates of decline in eGFR in men were similar to those in women (0.96 mL·min^-1·1.73 m^-2·yr^-1 vs. 0.91 mL·min^-1·1.73 m^-2·yr^-1). However, after referencing to the healthy group, the rates of decline in eGFR in men in the at-risk and CKD groups were greater faster than the corresponding rates in women (at-risk group: 0.10 mL·min^-1·1.73 m^-2·yr^-1 vs. -0.03 mL·min^-1·1.73 m^-2·yr^-1 and CKD group: 0.44 mL·min^-1·1.73 m^-2·yr^-1 vs. 0.15 mL·min^-1·1.73 m^-2·yr^-1).

Conclusion

To accurately assess gender differences in CKD progression rates, gender differences in age-related decline in GFR should be considered.

The science of Stewardship: due diligence for kidney donors and kidney function in living kidney donation--evaluation, determinants, and implications for outcomes

Living kidney donor transplantation is now a common treatment for ESRD because it provides excellent outcomes to transplant recipients and is considered a safe procedure for prospective donors. The short- and long-term safety of prospective donors is paramount to the continued success of this procedure. Whereas the initial experiences with living kidney donors mostly included the healthiest, the increase in the need for organs and the changing demographic characteristics of the general population have subtly reshaped the suitability for donation. Kidney function assessment is a critical component of the evaluation of prospective donors; therefore, special emphasis is usually placed on this aspect of the evaluation. At the same time, consideration of kidney function after donation is important because it assists with the determination of renal health in donors. This review summarizes the process of predonation kidney function assessment, determinants of pre- and postdonation renal function, and, importantly, the potential implications of kidney function to the long-term outcomes of kidney donors.

Prevalence of low glomerular filtration rate, proteinuria and associated risk factors in North India using Cockcroft-Gault and Modification of Diet in Renal Disease equation: an observational, cross-sectional study

BACKGROUND

Chronic kidney disease (CKD) is increasingly being recognized as an emerging public health problem in India. However, community based estimates of low glomerular filtration rate (GFR) and proteinuria are few. Validity of traditional serum creatinine based GFR estimating equations in South Asian subjects is also debatable. We intended to estimate and compare the prevalence of low GFR, proteinuria and associated risk factors in North India using Cockcroft-Gault (CG) and Modification of Diet In Renal Disease (MDRD) equation.

METHODS

A community based, cross-sectional study involving multistage random cluster sampling was done in Delhi and its surrounding regions. Adults > or = 20 years were surveyed. CG and MDRD equations were used to estimate GFR (eGFR). Low GFR was defined as eGFR < 60 ml/min/1.73 m2. Proteinuria (> or = 1+) was assessed using visually read dipsticks. Odds ratios, crude and adjusted, were calculated to ascertain associations between renal impairment, proteinuria and risk factors.

RESULTS

The study population had 3,155 males and 2,097 females. The mean age for low eGFR subjects was 54 years. The unstandardized prevalence of low eGFR was 13.3% by CG equation and 4.2% by MDRD equation. The prevalence estimates of MDRD equation were lower across gender and age groups when compared with CG equation estimates. There was a strong correlation but poor agreement between GFR estimates of two equations. The survey population had a 2.25% prevalence of proteinuria. In a multivariate logistic regression analysis; age above 60 years, female gender, low educational status, increased waist circumference, hypertension and diabetes were associated with low eGFR. Similar factors were also associated with proteinuria. Only 3.3% of subjects with renal impairment were aware of their disease.

CONCLUSION

The prevalence of low eGFR in North India is probably higher than previous estimates. There is a significant difference between GFR estimates derived from CG and MDRD equations. These equations may not be useful in epidemiological research. GFR estimating equations validated for South Asian populations are needed before reliable estimates of CKD prevalence can be obtained. Till then, primary prevention and management targeted at CKD risk factors must play a critical role in controlling rising CKD magnitude. Cost-benefit analysis of targeted screening programs is needed.

Estimation of glomerular filtration rate in South Asian healthy adult kidney donors

AIM

We evaluated the performance of serum creatinine based equations to estimate glomerular filtration rate (GFR) in South Asian healthy renal donors.

METHODS

GFR by 99mTc-diethylenetriamine pentaacetic acid (DTPA) renogram (mGFR) in 599 renal donors was measured. GFR was estimated using a six variable modification of diet in renal disease formula (MDRD1), a four variable MDRD formula (MDRD2), Cockcroft-Gault creatinine clearance (CG CrCl), Cockcroft-Gault glomerular filtration rate (CG GFR) and the Mayo Clinic formula (Mayo GFR). The performance of various prediction equations was compared for global bias, precision (R(2)) and accuracy (percentage of estimated GFR (eGFR) falling within 15% and 30% of mGFR).

RESULTS

The mean age was 37.4 +/- 11 years and 48.2% were male. The mGFR was 95.5 +/- 11.6 mL/min per 1.73 m(2). The bias (mL/min per 1.73 m(2)) was 7.5 +/- 0.9, -9.0 +/- 0.75, 13.1 +/- 0.9, 7.5 +/- 0.9 and 23.4 +/- 0.76 for CG CrCl, CG GFR, MDRD1, MDRD2 and Mayo GFR, respectively. R(2) was 0.082 for CG CrCl and MDRD1, 0.081 for CG GFR and MDRD2 and 0.045 for Mayo GFR. The percentages of eGFR falling within 15% and 30% of mGFR were 50.5 and 80.1 for CG CrCl, 65.8 and 84 for CG GFR, 50 and 74 for MDRD1, 54.3 and 80.1 for MDRD2 and 32 and 63.4 for Mayo GFR. Overall CG GFR performed better in estimating GFR in all subjects.

CONCLUSION

The CG GFR equation was better than other equations to estimate GFR in South Asian healthy renal donors. We propose a new equation derived from the regression model in our study population to estimate GFR in a South Asian healthy adult population.

Levels of GFR and protein-induced hyperfiltration in kidney donors: a single-center experience in India

BACKGROUND

Some studies have shown that the normal range of glomerular filtration rate (GFR) was lower in an Indian population than in western populations. To verify these findings and determine whether it is physiological or an expression of subclinical disease, we measured GFR in a cohort of healthy Indian adults by using more stringent criteria to define "healthy" than used in previous studies.

STUDY DESIGN

Cross-sectional study.

SETTING AND PARTICIPANTS

109 healthy adults being evaluated for kidney donation with normal blood pressure, body mass index, urinalysis results, and protein excretion and symmetrical function on radionuclide renogram. Subjects followed a vegetarian diet with 1 g/kg of protein intake for 10 days before the study.

PREDICTORS

Age, sex, relation to recipient (relative versus spouse), body surface area, body mass index, kidney size, serum creatinine level, and urinary protein-creatinine ratio. OUTCOME AND MEASUREMENTS: GFR measured as plasma clearance of technetium 99m diethyl-triamine-penta-acetic acid before and after amino-acid infusion (protein-induced hyperfiltration). Measurements were performed after a 12-hour fast.

RESULTS

Mean baseline GFR was 82.4 +/-12.7 mL/min/1.73 m(2) (95% confidence interval, 80.0 to 84.8). Mean stimulated GFR was 104.7 +/- 16.1 mL/min/1.73 m(2) (95% confidence interval, 101.6 to 107.8). Measured mean protein-induced hyperfiltration was 27.3% +/- 10.04% (range, 6.7% to 56%). In multivariable linear regression analysis, younger age, spousal donor, and larger average kidney size were associated with significantly greater baseline GFR, and only greater baseline GFR was associated significantly with stimulated GFR.

LIMITATIONS

Dietary protein intake was not measured; a habitual low-protein diet cannot be excluded as a cause of low GFR.

CONCLUSIONS

Basal GFR is significantly lower than the normal value of 120 to 130 mL/min/1.73 m(2) in western populations. The conventional cutoff value of 60 mL/min/1.73 m(2) for defining chronic kidney disease might not be appropriate in India.

Prevalence of chronic kidney disease (CKD) in the Japanese general population predicted by the MDRD equation modified by a Japanese coefficient

BACKGROUND

The number of patients with end-stage renal disease (ESRD) in Japan has continuously increased in the past three decades. In 2005, 36,063 patients whose average age was 66 years entered a new dialysis program. This large number of ESRD patients could be just the tip of the iceberg of an increasing number of patients with chronic kidney disease (CKD). However, to date, a nationwide epidemiological study has not been conducted yet to survey the CKD population.

METHODS

Data for 527,594 (male, 211,034; female, 316,560) participants were obtained from the general adult population aged over 20 years who received annual health check programs in 2000-2004, from seven different prefectures in Japan: Hokkaido, Fukushima, Ibaraki, Tokyo, Osaka, Fukuoka, and Okinawa prefectures. The glomerular filtration rate (GFR) for each participant was estimated from the serum creatinine values, using the abbreviated Modification of Diet in Renal Disease (MDRD) study equation modified by the Japanese coefficient.

RESULTS

The prevalences of CKD stage 3 in the study population, stratified by age groups of 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, and 80-89 years, were 1.4%, 3.6%, 10.8%, 15.9%, 31.8%, 44.0%, and 59.1%, respectively, predicting 19.1 million patients with stage 3 CKD in the Japanese general adult population of 103.2 million in 2004. CKD stage 4 + 5 was predicted in 200,000 patients in the Japanese general adult population. Comorbidity of hypertension, diabetes, and proteinuria increased as the estimated GFR (eGFR) decreased. The prevalence of concurrent CKD was significantly higher in hypertensive and diabetic populations than in the study population overall when CKD was defined as being present with an eGFR of less than 40 ml/min per 1.73 m(2) instead of less than 60 ml/min per 1.73 m(2).

CONCLUSIONS

About 20% of the Japanese adult population (i.e., approximately 19 million people) are predicted to have stage 3 to 5 CKD, as defined by a GFR of less than 60 ml/min per 1.73 m(2).

Differences in decline in GFR with age between males and females. Reference data on clearances of inulin and PAH in potential kidney donors

BACKGROUND

To ensure that potential kidney donors have no renal impairment, it is extremely important to have accurate methods for evaluating the glomerular filtration rate (GFR). The golden standard, clearance of inulin, has been used in the present study. The aim was to evaluate the effects of age and sex on renal function and present reference data.

METHODS

A total of 122 potential kidney donors, 62 females, aged 21-67 years, were investigated with the GFR and effective renal plasma flow (ERPF) determined by clearances of inulin and para-amino hippurate.

RESULTS

The mean +/- SD GFR and ERPF were 105 +/- 13 and 545 +/- 108 ml/min/1.73 m(2), respectively, and we found no difference between the males and females. When relating GFR and ERPF to age, however, a significant decline was found in GFR and ERPF in males, but not in females in the age range of 20-50 years. GFR fell by a mean of 8.7 ml/min/1.73 m(2) and ERPF by 90 ml/min/1.73 m(2) per decade in male donors.

CONCLUSION

With adequate methods for determining GFR and ERPF, a clear difference in the effect of age was seen between the sexes. Males showed a significant decrease between 20 and 50 years of age, which was not seen in females. Females seem to be protected in the pre-menopausal period probably by oestrogens. These results confirm clinically those found in rats.

Hypertension and kidney disease in Asia

PURPOSE OF REVIEW

Communicable diseases were traditionally the major cause of public health concern in Asian countries, most of which were less developed. With industrialization and associated lifestyle changes during the past few decades, however, noncommunicable diseases similar to those that affect Western societies have emerged in Asian countries. The purpose of the review was to examine recent evidence about the burden and factors associated with hypertension and chronic kidney disease (CKD) in Asian countries.

RECENT FINDINGS

Hypertension has become one of the leading causes of mortality in Asia. Although its prevalence continues to rise, it remains under-diagnosed and under-treated. CKD is becoming increasingly common mainly due to an increase in risk factors such as high blood pressure, diabetes, and obesity. Treatment of advanced CKD is overwhelmingly burdensome in a resource poor environment. Barriers to early detection of CKD in Asians include the fact that equations to estimate the glomerular filtration rate have not been validated in this population, and the uncertainty about appropriate glomerular filtration rate cutoff values to define CKD.

SUMMARY

Concerted efforts are needed to develop and implement cost-effective strategies for prevention and treatment of hypertension and CKD in Asian countries. More research is needed on these conditions in these populations.